Useful utilities

⭐

Air Fryer Converter — Oven to Air Fryer Settings

Convert oven temperature and time to air fryer settings (or back), using the standard −25°F/−15°C, 20-25% less time rule of thumb, plus a lookup table for common foods.

• Two-way conversion: oven → air fryer and air fryer → oven, in Fahrenheit or Celsius.
• Time shown as a range (75-80% of the source time), not a single misleading number.
• Built-in food lookup: frozen fries, chicken wings, chicken breast, salmon and roasted vegetables with typical air fryer temperature and time.

⭐

Area Converter

Convert area units instantly: square millimeters to square kilometers, hectares, square feet, square inches and acres.

• Eight units: mm², cm², m², hectares, km², in², ft², acres.
• Two-way live fields with instant swap.
• Common-values table tuned to real-estate and land sizes.

⭐

Aspect Ratio Calculator

Calculate the missing side for any aspect ratio — 16:9, 4:3, 21:9, 1:1 or custom — or simplify the ratio of two known dimensions.

• Common presets 16:9, 4:3, 21:9 and 1:1 plus a fully custom width:height ratio.
• Computes width from height or height from width, with decimal input supported.
• Simplifies any pair of dimensions via greatest common divisor, with the decimal ratio shown too.

⭐

Average Calculator

Paste a list of numbers and get the mean, median, mode, range, sum, min and max at once — or compute a weighted average with full steps.

• Mean, median, mode(s), range, sum, count, minimum and maximum from one list of numbers.
• Weighted average mode: value and weight pairs, one per line, with a step-by-step product table.
• Sorted copy of your list plus honest mode detection, including a clear "no mode" verdict.

⭐

BAC Calculator (Widmark Formula)

Estimate blood alcohol content from your drinks, body weight, sex and time elapsed using the classic Widmark formula, with every number shown — for education only, never for deciding whether to drive.

• Repeatable drink rows (volume + ABV%) with quick presets for beer (~5%), wine (~12%) and spirits (~40%).
• Body weight in kg or lb, sex-specific Widmark distribution ratio (r ≈ 0.68 men, ≈0.55 women), and hours elapsed since you started drinking.
• The fully substituted Widmark formula plus the resulting estimated BAC%, clamped at zero.

⭐

Barcode Generator

Generate Code 128, EAN-13, EAN-8, UPC-A and Code 39 barcodes with live validation and automatic check digits, downloadable as SVG or PNG.

• Five symbologies: Code 128 (auto subset B/C), EAN-13, EAN-8, UPC-A and Code 39.
• Live validation of allowed characters, length and check digit while you type.
• Human-readable digits rendered under the bars, with proper quiet zones.

⭐

Base64 / Hex / Binary Multi-Coder

Convert text or binary files to Base64, Hexadecimal, Binary representation and back.

• Convert Plain Text or Files to Base64, Hexadecimal, or Binary.
• Reconstruct files back from Base64 or Hex and download them.
• Interactive bitwise visualization chart mapping characters to bytes.

⭐

Calculator

A convenient web calculator for quick mathematical calculations in a stylish design.

• Operators +, -, *, /, %, ^ and parentheses.
• Functions sqrt, abs, sin, cos, tan, log, ln, min and max.
• Constants pi and e with clean formatted output.

⭐

BMI Calculator

Calculate your Body Mass Index in metric or imperial units and see your WHO category on a color scale, entirely in your browser.

• Color-coded BMI scale from underweight to obesity class III
• Healthy weight range calculated for your exact height
• Metric and imperial unit systems

⭐

Body Fat Calculator (US Navy Method)

Estimate your body fat percentage from tape measurements with the US Navy method, see your ACE category and fat/lean mass — right in your browser.

• US Navy circumference method with separate formulas for men and women
• ACE category classification: essential fat, athletes, fitness, average, obese
• Optional weight input to split your body into fat mass and lean mass in kg

⭐

Body Frame Size Calculator

Find your skeletal frame size — small, medium or large — from height and wrist circumference using the classic height-to-wrist ratio heuristic, right in your browser.

• Sex-specific cutoffs for men and women, each split into three brackets: small, medium and large frame.
• Unit toggle: enter height and wrist circumference in centimeters or inches, whichever tape measure you have.
• Copyable text summary of your ratio and resulting frame size.

⭐

Border Radius Generator

Design CSS border-radius visually: four independent corner sliders in px or percent, a link-all-corners shortcut for instant circles and pills, plus an organic blob mode with randomized shapes.

• Corners mode: independent top-left, top-right, bottom-right and bottom-left radius sliders, each switchable between px and percent units.
• Link-all-corners checkbox that drives every corner from one slider, plus a checkerboard preview on a light or dark backdrop so clipped corners stay visible.
• Blob mode with a Randomize button that builds organic eight-value slash-syntax shapes, shown large and ready to copy as CSS.

⭐

Bra Size Calculator & Converter

Estimate your bra size from underbust and bust measurements, or convert an existing size between US, UK, EU, FR and IT — plus its sister sizes.

• Traditional and modern band formulas from underbust, plus bust-minus-band mapped through an AA-to-L cup table.
• Size conversion between US, UK, EU, FR and IT band numbers and cup letters, using real published band and cup charts.
• Sister size calculator for whichever size you measured or converted: one band up/cup down, one band down/cup up.

⭐

Break-Even Calculator

Find the exact unit volume and revenue where fixed and variable costs stop exceeding sales, with a margin-of-safety readout and a revenue-vs-cost chart.

• Contribution margin per unit = price − variable cost, with a clear error if variable cost ever reaches or exceeds price.
• Break-even units = fixed costs ÷ contribution margin, and break-even revenue = break-even units × price, both shown with the formula substituted.
• Optional margin-of-safety readout: how far your actual or expected volume sits above or below the break-even point, in units, revenue and percent.

⭐

Caffeine Half-Life Calculator

Model how caffeine from your coffee, tea or energy drink decays over the next 12 hours and see how much is likely left when you go to bed.

• Preset doses: espresso (~63 mg), drip coffee (~95 mg), energy drink (~160 mg), black tea (~47 mg), plus a custom milligram field.
• Time-consumed and bedtime inputs, with the consumed time defaulting to right now.
• Bedtime callout: 'approximately X mg will likely still be in your system' as the key takeaway.

⭐

Calorie Calculator (BMR & TDEE)

Calculate your BMR, TDEE and daily calorie targets for weight loss, maintenance or gain with the Mifflin-St Jeor formula — right in your browser.

• BMR via the Mifflin-St Jeor equation for men and women
• TDEE with five activity levels from sedentary to very active
• Calorie targets for mild loss (−250), loss (−500), mild gain (+250) and gain (+500 kcal/day)

⭐

Cat Age Calculator (Cat Years to Human Years)

Convert your cat's age to human years with the AAHA/AAFP veterinary scale and see its life stage from kitten to geriatric — entirely in your browser.

• AAHA/AAFP scale: year one = 15 human years, year two = +9, then +4 per cat year
• Six veterinary life stages from kitten to geriatric, mapped to calendar age
• Indoor/outdoor selector with an evidence-based lifespan note for outdoor cats

⭐

Certificate & CSR Decoder (X.509 / PKCS#10)

Paste a PEM-encoded X.509 certificate or PKCS#10 CSR and see every field decoded — subject, issuer, validity, SANs, public key and fingerprint — entirely offline.

• Decodes subject, issuer, validity dates, public key algorithm and size, and Subject Alternative Names.
• Supports both X.509 certificates and PKCS#10 certificate signing requests, including SAN inside CSR extension requests.
• Honest about scope: does not check chain of trust or revocation (OCSP/CRL), and says so in the UI.

⭐

Child Growth Percentile Calculator (LMS Method)

Estimate a child's height or weight percentile using the real LMS statistical method behind official growth charts — entirely in your browser.

• Real LMS z-score formula with correct handling of the L = 0 special case, converted to a percentile via a numerical normal-CDF approximation.
• Illustrative L/M/S reference table at 12-month anchors from birth to 20 years, for boys and girls, height-for-age and weight-for-age, with linear interpolation for any exact age.
• Full transparency: displays the interpolated L, M, S values and the substituted formula, plus a plain-language explanation of what the percentile means.

⭐

Chmod Calculator

Convert Linux file permissions between rwx checkboxes, octal numbers and symbolic notation with a ready chmod command.

• Nine rwx checkboxes for owner, group and others synced live with the 3-digit octal value.
• Symbolic notation (-rwxr-xr-x) plus a per-class breakdown showing how each digit is composed from 4+2+1.
• Ready-to-copy chmod command and safety warnings for world-writable modes.

⭐

Circle Calculator

Enter any one measure of a circle — radius, diameter, circumference or area — and get the other three instantly, with every formula shown with your numbers substituted in.

• Solves from any of the four known values: radius, diameter, circumference or area.
• Shows each formula with substitution, e.g. C = 2πr = 2 × π × 5 ≈ 31.415927.
• Exact answers in terms of π (like A = 25π) whenever the radius or diameter is given.

⭐

Clothing Size Converter

Convert clothing sizes between US, UK, EU, Italian, French, Japanese and international S–XXL scales for dresses, shirts, suits and trousers.

• Seven regional scales, including Italian and French numbering and international S–XXL.
• Size picker adapts to the chosen chart and region, so only real chart sizes can be selected.
• Full chart row for every conversion, not just the single target size.

⭐

Code Formatter

Fast alignment and formatting of HTML, CSS, JavaScript and TypeScript code offline.

• Processes text payloads up to 5MB smoothly.
• Fast parsing: Normalizes spacing, braces, and line breaks in milliseconds.
• Instant clipboard copy and raw source code download integrations.

⭐

Code Minifier

Minify CSS, JavaScript, HTML or JSON in the browser: strip comments and whitespace, see the size saved instantly.

• Four languages in one tool: CSS, JavaScript, HTML and JSON.
• String, template-literal and regex-aware JavaScript scanner that never breaks literals.
• HTML mode preserves pre, textarea, script and style content verbatim.

⭐

Color Format Converter

Convert any color between HEX, RGB, HSL and CMYK notation with a live preview swatch — right in your browser.

• Converts between HEX, RGB, HSL and CMYK color models.
• Native color picker that fills the value field in the selected format.
• Live preview swatch plus one-click copy of all four notations.

⭐

Compound Interest Calculator

See how an investment grows with compound interest: final balance, total contributed and interest earned, with a year-by-year growth table.

• Classic FV = P·(1+r/n)^(n·t) growth with daily, monthly, quarterly or annual compounding.
• Optional monthly contribution added at the end of each month and compounded at the equivalent monthly rate.
• Year-by-year schedule: balance, total contributed and interest for every year up to 10, then every 5th year.

⭐

Concrete Calculator — Bags Needed for Slabs, Footings & Posts

Work out how much concrete a slab, footing, column pour or a batch of fence post holes needs: pick the shape, enter its real dimensions, and get the volume in cubic yards and cubic meters plus the number of pre-mixed bags to buy.

• Slab, footing, column and post-holes shapes with shape-specific fields
• Imperial (ft + in) or metric (m + cm) units, paired to how each dimension is normally measured
• Cubic yard and cubic meter volume shown side by side

⭐

Cooking Measurement Converter

Convert cups, tablespoons, teaspoons, milliliters, grams and ounces with real ingredient densities — because a cup of flour does not weigh a cup of sugar.

• Twelve ingredients with typical household densities: water, milk, flour, sugar, brown sugar, powdered sugar, butter, oil, honey, cocoa, rice, salt.
• Eight units: cup (240 ml), tablespoon (15 ml), teaspoon (5 ml), ml, l, g, kg, oz (28.3495 g).
• Every volume ↔ weight result names the density it used, so you can sanity-check against your recipe.

⭐

Crontab Generator

Build cron expressions with dropdowns and instantly see a plain-language schedule plus the next 5 real run times.

• Per-field builders for minute, hour, day of month, month and day of week: every value, every N, or specific lists and ranges (0,30 or 9-17).
• Live human-readable explanation of the schedule with localized month and weekday names.
• Next 5 run times computed with real calendar math, including the POSIX day-of-month OR day-of-week rule.

⭐

CSS Animated Gradient Border Generator

Generate a smoothly rotating rainbow gradient border that correctly respects border-radius, built with @property, conic-gradient and mask-composite — copy the real CSS, watch it spin live.

• Border width, border-radius and rotation duration sliders plus a clockwise/counter-clockwise direction switch, all updating the live preview instantly.
• A color stop editor for 2 to 5 gradient colors — add, remove or repick any stop and the conic-gradient sweep updates on every change.
• Copyable CSS block with the full @property registration, the ::before ring rules and the @keyframes rotation, ready to paste as-is.

⭐

CSS Box Shadow Generator

Build CSS box-shadow code visually: sliders for offset, blur, spread, color with opacity, inset mode and up to four layers with a live preview.

• Sliders for X/Y offset, blur and spread with live pixel readouts, plus a color picker with a separate opacity slider.
• Inset checkbox and a layer list: add, select and remove up to four shadow layers.
• Copyable box-shadow CSS line covering all layers, previewed on a switchable light or dark backdrop.

⭐

CSS Clamp() Calculator

Compute a real fluid CSS clamp() value from a min and max size across two viewport widths, with the slope and intersection shown step by step and a live resize preview.

• Real fluid-typography math: slope, vw coefficient and y-axis intersection shown explicitly, not just the final clamp() line.
• Live preview: drag the viewport-width slider to watch sample text resize exactly as it would while a real browser window is resized.
• Type-scale mode: a base size and a ratio from 1.125 to 1.5 generate six fluid clamp() steps — small, base, h4, h3, h2, h1 — as copy-ready CSS.

⭐

CSS Clip-Path Generator

Draw arbitrary polygon shapes — including concave notches — by dragging points on a live preview box or your own uploaded image, and copy the resulting CSS clip-path: polygon(...) value.

• Draggable point handles (mouse, touch and arrow-key nudging) with live-updating clip-path: polygon(...) output as you move them.
• Click near any edge to insert a new point there, double-click a point to remove it (a minimum of 3 points is always kept).
• Presets for arrow, star, hexagon, speech-bubble and ticket-stub shapes — including genuinely concave, non-convex outlines — plus optional image upload so you can preview the clip on your own picture.

⭐

CSS Filter Generator

Build a reorderable chain of CSS filter() and backdrop-filter() functions and preview it live on your own uploaded photo, with a copyable CSS line and PNG export.

• Nine chainable filter functions — blur, brightness, contrast, saturate, hue-rotate, sepia, grayscale, invert and drop-shadow — each with its own slider and native drag handle.
• Live preview image with a instant-updating copyable filter: CSS line, plus a smaller backdrop-filter chain and demo panel for the frosted-glass look.
• One-click PNG export renders the uploaded photo through the exact same filter string with Canvas 2D's ctx.filter, matching the on-screen preview pixel for pixel.

⭐

CSS Flexbox Generator

Build a CSS flexbox layout visually: flex-direction, justify-content, align-items, flex-wrap and gap on the container, plus per-child flex-grow, flex-shrink and flex-basis, all with a live preview and copyable CSS.

• Container controls: flex-direction, justify-content, align-items, flex-wrap and a gap input in pixels, applied live to the preview.
• Three color-coded child boxes by default (add up to eight, remove down to two), each with its own flex-grow, flex-shrink and flex-basis fields.
• Copyable CSS block with a .flex-container rule plus one .flex-item-N rule per child that has non-default flex properties.

⭐

CSS Gradient Generator

Build CSS gradients visually: linear, radial or conic type, angle slider and up to six color stops with a live full-width preview and copyable code.

• Gradient type select (linear, radial, conic) with an angle slider for linear and conic modes.
• Color stop list: two stops to start, add or remove up to six, each with its own color picker and position in percent.
• Copyable background CSS line plus ready-made preset pages for sunset, ocean and pastel gradients.

⭐

CSS Grid Generator

Design CSS Grid layouts visually: set columns, rows and gap, then type area names into cells to build grid-template-areas — with a live preview and copyable CSS and HTML.

• Number inputs for 1–6 columns and rows, plus separate column-gap and row-gap controls that combine into one gap value when they match.
• A named-areas mode: type an area name straight into any cell of the live grid; the tool builds a valid grid-template-areas string and warns when names do not form clean rectangles.
• Copyable CSS block (display: grid, grid-template-columns/rows, gap, grid-template-areas) plus a matching HTML skeleton with one grid-area div per named region.

⭐

CSS Keyframe Animation Generator

Build real @keyframes animations on a multi-track timeline — transform, opacity and background-color stops per track — with a draggable playhead that shows the exact interpolated mid-animation state.

• Multi-track timeline for transform (translateX, translateY, rotate, scale), opacity and background-color, each with its own draggable stops.
• Real linear interpolation — numeric properties and per-channel RGB for colors — drives the scrub-preview between any two stops on a track.
• A Play button applies the actual generated @keyframes CSS to the preview via a dynamically injected stylesheet, plus a copyable full @keyframes + animation shorthand output.

⭐

CSS Pattern Background Generator

Build tileable stripes, dots, checkerboard, grid, diagonal crosshatch and triangle backgrounds from real layered CSS gradients — zero images — or export the same pattern as an SVG <pattern> for use inside SVG documents.

• Six pattern types — stripes, dots, checkerboard, grid, diagonal crosshatch and triangles — each with its own relevant controls (colors, size/spacing, angle where it applies).
• CSS mode outputs a ready background-color/background-image/background-size block; SVG mode outputs an equivalent <pattern> definition with a copy button and a direct .svg download.
• Every control rebuilds the live CSS on input, so the tiled preview and the copyable code stay in sync at all times.

⭐

CSS Scrollbar Generator

Style a scrollbar's width, track, thumb and hover color, then see the real WebKit result next to the real Firefox result — two genuinely different browser systems, side by side.

• Shared controls — width, track color, thumb color, hover color, thumb corner radius — drive both engines from the same inputs.
• Honest scrollbar-width mapping: Firefox only supports thin, auto or none, so the exact pixel value you pick is mapped to the closest real keyword and shown next to your input.
• Combined, copyable CSS output with both the WebKit pseudo-element rules and the Firefox standard properties, clearly commented.

⭐

CSS Text Effects Generator

Type your own text and preview real neon-glow, 3D-extrude, letterpress, outlined and gradient-fill CSS effects live, with parameters computed by real math and a copyable CSS block.

• Five real effects — neon glow, 3D-extrude, letterpress/emboss, outlined and gradient-fill — each with its own parameter controls (colors, depth/angle sliders, gradient stops).
• Neon glow includes an optional flicker animation with a randomized `@keyframes` opacity pattern you can reshuffle without touching CSS by hand.
• 3D-extrude lets you drag depth (number of layers) and angle independently; every layer's pixel offset and progressively darker shade recompute live.

⭐

Cubic Bezier Generator

Design a custom CSS cubic-bezier() timing function by dragging two control points, preview it live against a linear reference, then copy the ready value.

• Draggable SVG curve editor with two handles (P1 and P2) plus editable x1/y1/x2/y2 number inputs for pixel-precise values.
• Looping animation preview comparing your custom cubic-bezier() timing to a linear reference ball, so you can see the easing, not just read it.
• Copyable cubic-bezier(x1, y1, x2, y2) string ready for transition-timing-function or animation-timing-function, plus preset pages for ease-in-out, bounce and Material Design's standard curve.

⭐

Curl Converter

Convert curl commands into ready-to-run Python, JavaScript fetch, Node axios, PHP and Go code — locally in your browser.

• Five targets: Python requests, JavaScript fetch, Node.js axios, PHP cURL and Go net/http.
• JSON bodies are detected and rendered as native dict/object literals, not opaque strings; -u becomes proper basic auth, -F becomes multipart form code.
• Syntax-highlighted output with one-click copy and download under the right file name (request.py, main.go…).

⭐

JSON / YAML / TOML / XML Serialization Converter

Bidirectional conversion between JSON, XML, YAML, and CSV config serialization formats fully client-side.

• Bidirectional conversion for JSON, XML, YAML, and CSV.
• Auto-generation of TypeScript declaration types.
• Offline serialization parser running locally.

⭐

Data Storage Converter

Convert data storage units instantly: bits, bytes, KB, MB, GB, TB and the binary KiB, MiB, GiB, TiB — with the 1000 vs 1024 distinction made explicit.

• Ten units: bit, byte, KB, MB, GB, TB, KiB, MiB, GiB, TiB.
• Exact factors: decimal units use powers of 1,000, binary units use powers of 1,024, and 1 byte = 8 bits.
• One-click copy of the conversion result.

⭐

Dead Pixel Test

Fill your screen with solid white, black, red, green, blue and gray to spot dead or stuck pixels — plus a flashing fixer that may revive stuck ones.

• Fullscreen test cycle of white, black, red, green, blue and gray — advance by click or arrow keys, exit with Esc.
• Stuck-pixel fixer: a small draggable region flashes red, green, blue, white and black on every animation frame.
• Works even when fullscreen is blocked: the test falls back to filling the browser viewport.

⭐

Debt Payoff Calculator

Plan how up to five debts get paid off with the snowball or avalanche strategy: debt-free date, total interest, payoff order and the savings between the two.

• Up to five debts, each with an optional name, balance, APR and minimum monthly payment.
• Month-by-month simulation: interest = balance × APR/12, minimums to every debt, extra money and freed-up minimums to the target debt.
• Snowball (smallest balance first) and avalanche (highest APR first) strategies with a payoff order list.

⭐

Decking Calculator — Deck Boards & Joists Needed

Work out how many linear feet of decking boards and how many joists a deck needs, using real actual-vs-nominal lumber dimensions, a board expansion gap, standard 16in/24in on-center joist spacing, and a waste allowance for cuts.

• Real actual-vs-nominal lumber dimension table (5/4×6, 2×4, 2×6, 2×8)
• Board-run direction toggle plus expansion gap and waste allowance
• Joist count from standard 16in/24in on-center framing spacing

⭐

Depreciation Calculator

Generate a full straight-line or declining-balance depreciation schedule for an asset, year by year, with a chart comparing both methods' book value over time.

• Straight-line method: constant annualDepreciation = (cost − salvage) ÷ usefulLife every year.
• Declining-balance method with a selectable rate multiplier (2 = double-declining, 1.5 = 150%-declining, or any custom multiplier).
• Declining balance is floored at the salvage value: the final depreciating year is capped so book value never drops below salvage.

⭐

Diceware Passphrase Generator — Random Word Passphrases

Generate strong, memorable passphrases built from random real words using the Diceware method — true cryptographic randomness, with the actual entropy in bits shown honestly.

• 4 to 10 words per passphrase from a curated, deduplicated list of ordinary English words, with space, hyphen or dot separators.
• Optional capitalization and an optional random 2-digit number, each with its true entropy contribution stated separately.
• Live entropy readout showing the exact formula: word count times bits-per-word, plus any bonus from the number, equals total bits.

⭐

Discount Calculator

Calculate the sale price after a discount, see how much you save, and stack a second discount on top.

• Sale price and amount saved from any price and percent off.
• Optional second stacked discount (extra % off the reduced price).
• Effective total discount percent for stacked deals.

⭐

Dog Age Calculator (Dog Years to Human Years)

Convert your dog's age to human years with two published models — the AVMA/AKC size-class table and the 2019 UCSD epigenetic formula — plus a life-stage label.

• AVMA/AKC size-class table: 15 + 9 human years for the first two years, then 4–6 per year by size
• UCSD 2019 epigenetic clock: 16 × ln(age) + 31, derived from Labrador DNA methylation data
• Life-stage label from puppy to senior, with the senior threshold adjusted per size class

⭐

Drywall Calculator — Sheets & Screws Needed

Add up wall and ceiling sections — by length × height or a direct area, as many rows as you need — and get the number of standard 4×8ft or 4×12ft drywall sheets to buy, plus an optional honest rule-of-thumb screw-count estimate.

• Repeatable section rows: length × height or a direct area per row, add or remove freely
• Real 4×8ft (32 sq ft) / 4×12ft (48 sq ft) trade sheet sizes with a waste allowance
• Optional honest rule-of-thumb screw-count estimate, clearly labeled as an estimate

⭐

Electricity Cost Calculator — Appliance Running Costs

See what any appliance adds to your electricity bill: pick a device or enter watts, hours per day and your price per kWh to get energy use and cost per day, month and year.

• Appliance picker with editable wattage and hours per day
• Energy in kWh for a day, a 30-day month or a 365-day year
• Cost breakdown per day, month and year in your currency

⭐

AES-GCM Secure Encrypted Notepad

Author, encrypt, and decrypt custom text files locally using secure AES-GCM 256-bit password-based encryption.

• Offline AES-GCM 256-bit text encryption and decryption.
• Self-contained executable HTML notes exporter.
• Idle inactivity automatic shredder safety.

⭐

ENV Diff Checker

Compare two .env files (staging vs. production, before vs. after a deploy) and see exactly which keys were added, removed or changed, with secret-looking values masked automatically.

• Two side-by-side textareas (File A / File B) and an Execute button that produces a clear diff table: key, status, old value and new value.
• Keys are classified as added, removed or changed; identical keys are hidden by default behind a 'show unchanged' toggle, with a one-line summary count above the table.
• Masking is computed independently for the old and new value of every row, so a secret that changed between environments shows two separately masked values, not one shared guess.

⭐

20-20-20 Eye Strain Timer

A live background timer for the American Optometric Association's 20-20-20 rule: every 20 minutes, look at something 20 feet away for 20 seconds, with a real 20-second break countdown when it's time.

• 20-minute countdown to the next break, followed automatically by a distinct 20-second break view with a large circular ring countdown.
• A gentle WebAudio chime plays at the start of every break — no audio files, generated live by your browser.
• Simple start, pause and reset controls, plus a running count of breaks completed in the session.

⭐

Fence Calculator — Posts, Rails & Pickets from a Linear Run

Work out how many posts, rails and pickets a fence needs from its total linear run: pick a post spacing, account for gates as a real deduction from the run, and get a materials count that honestly includes the classic "N spaces need N+1 posts" fencepost problem.

• Real discrete-counting math (posts, rails, pickets) instead of the area/volume math this site's other material calculators use
• The "+1 post" rule made explicit, plus separate gate-post handling
• Picket-fence or rail-only mode, with picket count from width and gap spacing

⭐

AES-256 File Encryptor

Password-protect any file into a portable AES-256-GCM encrypted bundle, and decrypt it back later with the same password, entirely offline.

• Encrypt any file type (images, PDFs, archives, anything) into a downloadable .enc bundle.
• Decrypt a .enc bundle back to the original file with the correct password.
• Wrong-password and corrupted-file detection via AES-GCM's built-in authentication tag.

⭐

Firewood Cord Calculator — Stack Dimensions & Face Cord Conversion

Work out how many cords a stack of firewood is from its length, width and height — or convert 'face cords' (a.k.a. ricks) of a given log length into standardized full cords, since a face cord's size always depends on how the logs were cut.

• Stack-dimensions mode: length x width x height in feet/meters, converted to cubic feet and divided by 128 for the legally standardized cord count
• Face-cord (rick) conversion mode: N face cords of a chosen log length turn into equivalent full cords via the exact same volume ÷ 128 arithmetic, not a separate rule of thumb
• Preset log lengths (12/16/18/24 in) plus a fully custom length in inches or centimeters, since face cord size is defined entirely by how long the logs are cut

⭐

Fraction Calculator

Add, subtract, multiply and divide fractions and mixed numbers, simplify them, and convert fraction to decimal and back — with steps.

• Four operations on two fractions, including mixed numbers
• Fraction ↔ decimal conversion with repeating-period notation
• Step-by-step explanations with GCD and LCM

⭐

Freelance Rate Calculator

Reverse-engineer the day rate or hourly rate you must charge as a freelancer or consultant from your target take-home income, overhead, taxes and realistic non-billable time.

• Grosses up your desired net income for business overhead and a self-employment tax reserve to get the revenue you actually need to bill.
• Splits the year into working days, non-billable days (vacation, admin, marketing) and the billable days left over.
• Computes the day rate and hourly rate both at 100% utilization and at your realistic booking rate, with the formulas substituted step by step.

⭐

Fuel Cost Calculator — Trip Cost by Distance & Consumption

Calculate how much fuel a trip needs and what it costs from distance, consumption (L/100km, km/L or MPG) and fuel price — with cost per passenger.

• Distance in kilometers or miles, price per liter or US gallon
• Fuel amount shown in both liters and gallons
• Optional cost split across up to 99 passengers

⭐

Gamepad Tester

Test any controller online: press buttons to light them up, watch live stick crosshairs, measure stick drift against a deadzone circle and try vibration.

• Live buttons grid polled from navigator.getGamepads() — pressed state plus fractional values for analog triggers.
• Two stick crosshairs with a toggleable deadzone circle, per-stick idle offset readout and raw axis values.
• Dual-rumble vibration test through the controller's vibration actuator, feature-detected with an honest not-supported note.

⭐

GCF & LCM Calculator

Greatest common factor and least common multiple of 2–10 numbers, with the Euclidean algorithm shown step by step and the prime factorization of every number.

• GCF and LCM of 2 to 10 whole numbers in one run.
• Step-by-step Euclidean algorithm and the lcm(a, b) = a × b ÷ gcd(a, b) working shown.
• Prime factorization of every number in exponent form (48 = 2⁴ × 3).

⭐

Glassmorphism Generator

Dial in a frosted-glass card — blur, tint, border highlight, corner radius and shadow — previewed floating over a genuinely animated background so blur quality is visible in motion.

• Blur, tint color/opacity, border highlight color/opacity/width, corner radius and shadow softness controls, all live.
• An animated CSS gradient background behind the card via a real @keyframes background-position loop, so frosted blur is visible against genuine motion.
• Copyable CSS including a real @supports not (backdrop-filter) fallback block with an automatically higher opacity, commented and explained.

⭐

GPA Calculator — Weighted Grade Point Average

Calculate your credit-weighted GPA from letter grades on the 4.0, 5.0 or 100-point scale, with instant conversion between scales.

• Editable course table with add/remove rows
• Letter grades A to F with plus/minus steps
• Result shown with equivalents on the other scales

⭐

Grade Calculator

Find the final exam score you need to reach your desired grade, or compute a weighted average of up to five grades.

• Required final exam score from your current grade, desired grade and the exam's weight: (desired − current·(1−w)) / w.
• Friendly verdicts when the target is already secured (even a 0 keeps it) or not achievable (even a perfect 100 falls short).
• Weighted average mode for up to five grade + weight pairs, with the full breakdown shown.

⭐

Half-Life Decay Calculator

Solve the exponential decay equation N(t) = N0 x (1/2)^(t/half-life) for any substance, isotope or drug you name — enter any three of remaining amount, initial amount, elapsed time and half-life, and it solves for the fourth with the rearranged formula shown step by step.

• Generic exponential decay solver — N = N0 x (1/2)^(t / half-life) — algebraically rearranged for whichever of N, N0, t or half-life is unknown.
• Step-by-step derivation using your actual numbers, including the change-of-base identity log2(x) = ln(x) / ln(2) when solving for elapsed time or half-life.
• SVG decay curve sampled at about 50 points from t=0 to four half-lives, with the known/solved point marked.

⭐

HAR File Waterfall Analyzer

Upload a .har file exported from your browser's DevTools to see a real request waterfall built from each request's own timing data, plus checks for missing cache headers, uncompressed responses, and render-blocking scripts.

• Canvas-rendered request waterfall colored by timing phase, with DOMContentLoaded and Load markers.
• Three rule-based finding groups: missing cache headers, uncompressed text responses, and render-blocking candidates.
• Fully offline: the uploaded .har file is parsed and analyzed entirely in your browser — nothing is sent anywhere.

⭐

Cryptographic Checksum Hash Generator

Generate and compare multiple cryptographic hash checksums (MD5, SHA-1, SHA-256, SHA-512) for text and large files locally.

• Local calculations for MD5, SHA-1, SHA-256, and SHA-512.
• Supports large files (up to 2GB) without freezing browser tabs.
• Interactive checksum comparison with colored mismatch indicators.

⭐

Heart Rate Zone Calculator

Calculate your five heart rate training zones from age using the Tanaka formula, with optional Karvonen (heart rate reserve) targets from your resting pulse.

• Five color-coded zones: recovery, easy, aerobic, threshold and maximum (50–100% of max HR).
• Tanaka max HR as the primary estimate, classic 220 − age shown for reference.
• Optional resting heart rate input adds Karvonen (HRR) ranges to every zone.

⭐

HMAC Generator & Verifier

Generate and verify HMAC message authentication codes with SHA-256, SHA-384, SHA-512, or SHA-1 using a secret key, entirely in your browser.

• Sign text or files with HMAC-SHA256, HMAC-SHA384, HMAC-SHA512, or HMAC-SHA1.
• Accepts the secret key as UTF-8 text, hex, or Base64, and outputs the signature as hex or Base64.
• Verify mode compares a provided signature against the computed one with a clear match/mismatch indicator.

⭐

HTML Accessibility Auditor

Paste raw HTML and get a real WCAG accessibility audit: a hand-built DOM walker checks images, form labels, heading order and link text, plus a genuine relative-luminance contrast-ratio calculator scored against the real AA/AAA thresholds — no external library, nothing sent anywhere.

• Walks a real DOM parsed with the browser's native DOMParser: flags <img> missing an alt attribute (while correctly treating alt="" as an intentional, compliant decorative marker), and <input>/<select>/<textarea> with no <label for>, no wrapping <label>, and no aria-label/aria-labelledby.
• Checks heading structure for a missing or duplicated <h1> and for skipped levels (an <h1> followed directly by an <h3> with no <h2> in between) using the actual heading order in the document.
• Computes real WCAG contrast ratios for any element with an inline color + background-color style, reading its font-size/font-weight to apply the correct 'large text' threshold, and scores the result against all four real thresholds: 4.5:1 (AA normal), 3:1 (AA large), 7:1 (AAA normal) and 4.5:1 (AAA large).

⭐

HTML Table Generator

Build an HTML table visually by clicking cells and typing — get clean, semantic table markup with a live preview, no format to paste or convert.

• Editable grid: add or remove rows and columns with one click, and type directly into any cell.
• Style toggles for header row, zebra striping, cell borders, and a mobile-friendly horizontal-scroll wrapper.
• Live rendered preview next to indented, copy-ready HTML, plus a one-click copy button.

⭐

Ideal Weight Calculator

Calculate your ideal body weight from height and sex with four classic formulas — Devine, Robinson, Miller and Hamwi — plus the healthy BMI range, right in your browser.

• Devine, Robinson, Miller and Hamwi formulas in one comparison
• Healthy BMI weight range for your exact height
• Copyable text summary of all results

⭐

IEEE-754 Float Visualizer

See exactly how a decimal number is stored as an IEEE-754 float — sign bit, exponent bits and mantissa bits — and why numbers like 0.1 aren't stored exactly.

• Toggle between 32-bit single precision and 64-bit double precision.
• Color-coded bit grid renders the sign, exponent and mantissa regions as individual bit boxes.
• Step-by-step derivation text (capped to a readable number of iterations) while the bit grid always shows the true, full bit width.

⭐

Inflation Calculator

See what a dollar amount from any year between 1913 and 2025 is worth in another year using official US CPI data, or project a future value at a custom inflation rate.

• Historical mode: BLS CPI-U annual averages for 1913–2025, bundled statically.
• Projection mode: compound any amount forward at a custom annual rate for up to 100 years.
• Shows total change in percent, annualized rate and what the amount will still buy.

⭐

Insulation R-Value Calculator — Assembly R-Value vs. Climate Zone

Stack as many insulation layers as your assembly actually has — material type and thickness per layer — and add them into a total R-value, then compare that total against published US DOE climate-zone recommendations for attics, walls and floors to see a plain meets/below-recommended verdict.

• Repeatable insulation-layer rows: material type and thickness per layer, add or remove freely, summed into one assembly R-value
• Real R-value-per-inch reference figures for 7 common materials plus a custom-value option
• Comparison against a static reference table of published DOE climate-zone recommended R-values for attic, wall or floor

⭐

Intermittent Fasting Timer

Pick a 16:8, 18:6, 20:4, OMAD or 5:2 fasting protocol and watch a live countdown to your next eating or fasting window — a scheduling tool, not a health claim.

• Protocol picker (16:8 / 18:6 / 20:4 / OMAD / 5:2) plus a 'window started at' time so the countdown matches your real schedule.
• Live HH:MM:SS countdown with a current-phase label, the next transition time, and a phase-change beep, mirrored into the browser tab title.
• 5:2 mode swaps the countdown for static explanatory copy and a day-of-week picker for your two light-eating days — no invented hourly clock for a weekly protocol.

⭐

JSON Diff Checker

Compare two JSON payloads by structure, not by text: see every added, removed and changed key on its own path, entirely in your browser.

• Live, two-pane comparison: edit the Original or Changed JSON and the diff list updates instantly, no button to press.
• Path-based diff list with added/removed/changed/unchanged entries, color-coded and collapsible via a 'show unchanged' toggle.
• Optional 'sort keys before comparing' mode that walks and lists object keys in canonical alphabetical order for a stable, deterministic reading order.

⭐

JSON Formatter

Beautifully format, validate, compress and sort JSON data locally.

• Format spacing (2/4 spaces, tabs) or minify to single-line JSON.
• Handles nested dictionaries and arrays recursively.
• Instant single-click copy-to-clipboard integration.

⭐

JSON to TypeScript Converter

Convert JSON into TypeScript interfaces, type aliases or a Zod schema live, with real optional-field detection across arrays.

• Recursively infers a named interface for every nested object and every array of objects.
• Merges array element shapes field by field, so a field only present in some items becomes optional.
• Live conversion on every keystroke, with invalid JSON reported inline instead of crashing the page.

⭐

JWK ⇄ PEM Key Converter

Convert cryptographic keys between JWK and PEM format using the real Web Crypto API, decode algorithm/curve/size, and compute the RFC 7638 JWK thumbprint.

• PEM → JWK and JWK → PEM in both directions, for RSA (RSASSA-PKCS1-v1_5), EC (P-256/P-384/P-521), and Ed25519/X25519 where the browser supports them.
• Honest feature detection: Ed25519/X25519 support is probed with a real generateKey() call, and the tool says plainly when your browser lacks it instead of faking a result.
• Key info panel shows key type (public/private), algorithm, curve or modulus size, and the RFC 7638 thumbprint, plus one-click copy and download of the converted key.

⭐

JWT Token Debugger

Decode, inspect and verify the signatures of JSON Web Tokens fully client-side.

• Auto-decode Header and Payload JSON structures.
• Check expiration validity and signature validation.
• Edit claims and re-sign tokens with local HMAC secret keys.

⭐

Keyboard Tester

Press any key and watch it light up on an on-screen keyboard: check every switch, count simultaneous keys and spot dead or chattering keys.

• On-screen ANSI keyboard that reacts to real keydown and keyup events via KeyboardEvent.code.
• Press history line, total press counter and a dedicated spacebar counter.
• Tab, Space, F-keys and quote keys are intercepted during the test so the browser does not hijack them.

⭐

Length Converter

Convert length units instantly: millimeters, centimeters, meters, kilometers, inches, feet, yards and miles.

• Eight units: mm, cm, m, km, inches, feet, yards, miles.
• Two-way live fields with one-click unit swap.
• Common-values table that follows your selected units.

⭐

Loan Calculator

Calculate the monthly payment, total cost and total interest of any loan, with a first-year amortization breakdown.

• Monthly annuity payment from the amount, annual rate and term.
• Term entered in months or years, including fractional years like 2.5.
• Total paid and total interest over the whole life of the loan.

⭐

Long Division Calculator

Divide two whole numbers with the full long-division bracket drawn step by step: every multiply, subtract and bring-down, quotient with remainder, decimal expansion and mixed number.

• Full worked bracket: quotient on top, every product, subtraction line and bring-down row aligned by digit.
• Quotient with remainder, decimal expansion to 10 places with repeating digits overlined, and the mixed-number form.
• One-click copy of the whole worked solution as plain text.

⭐

Macro Calculator (Protein, Carbs & Fat)

Calculate your daily protein, carbs and fat in grams from your calorie needs, goal and diet style — Mifflin-St Jeor based, right in your browser.

• Daily calorie budget for maintenance, weight loss (−500 kcal) or muscle gain (+300 kcal)
• Protein, carbs and fat in grams at 4/4/9 kcal per gram
• Per-meal breakdown for 3 or 4 meals a day

⭐

Magic Bytes & Binary Header Doctor

Inspect file magic signatures, view raw hex/ASCII headers, and repair corrupted binary file headers client-side.

• 128-byte hex and ASCII grid viewer.
• MIME signature identifier library.
• One-click header repair doctor and download reconstruction.

⭐

Margin Calculator

Calculate revenue, profit, margin and markup from a cost plus any one of selling price, margin percent or markup percent — with both formulas shown.

• Enter the cost plus any one of revenue, margin % or markup % — the calculator solves for the rest.
• Margin computed as profit ÷ revenue, markup as profit ÷ cost, both always displayed with plugged-in numbers.
• Handles loss-making prices too: negative profit yields negative margin and markup.

⭐

Markdown Converter

Instant two-way conversion between Markdown markup and plain HTML.

• Bidirectional conversion (MD <-> HTML).
• Live side-by-side preview window.
• Syntax highlighted output textareas.

⭐

Markdown Table Generator

Build a Markdown table visually: click a cell and type, add rows and columns, set per-column alignment, and copy the ready GFM table.

• Editable spreadsheet-like grid with add/remove column and add/remove row controls.
• Left/center/right alignment picker per column, mapped to the GFM separator row.
• Paste CSV or TSV to import rows straight from Excel, Google Sheets or a .csv file, with a proper quoted-field parser.

⭐

Math Worksheet Generator

Generate a printable A4 arithmetic worksheet for kids — addition, subtraction, multiplication, division and number-house problems, plus a matching answer key.

• Five problem types: addition, subtraction, multiplication, division and number houses (classic composition/decomposition boxes), any combination at once
• Configurable operand range (0-1000 guard) that bounds every operand, plus an honest "allow negative numbers" toggle that only changes subtraction, the one operation where a negative result is meaningful
• "Convenient numbers" toggle keeps one multiplication factor times-table-friendly (<=10); division is always exact regardless of this toggle, computed divisor-and-quotient-first, never filtered after the fact

⭐

Matrix Calculator

Add, subtract, multiply and transpose 2×2 or 3×3 matrices, plus find the determinant and inverse with the full cofactor-expansion trace — minors, signed cofactors, the adjugate and every step shown as exact fractions.

• Handles 2×2 and 3×3 matrices for addition, subtraction, multiplication, transpose, determinant and inverse.
• The 3×3 determinant and inverse expand the real cofactor method: nine minors, the +/−/+ sign checkerboard, the adjugate matrix, then division by the determinant.
• All arithmetic — sums, dot products, minors, cofactors, the final division — is done with exact reduced fractions, never floating-point decimals.

⭐

Meat Cooking Time Calculator

Estimate roasting time for turkey, chicken, beef, pork, ham and lamb from weight and oven temperature, with USDA safe internal temperatures and rest times.

• Seven meat profiles with honest per-pound roasting rates at the USDA-standard 325°F (163°C) oven, converted live for kilograms.
• Doneness choice for beef roast (rare through well done) with the USDA 145°F (63°C) minimum always shown alongside it.
• Oven-temperature adjustment for 325°F, 350°F and 400°F, safe internal temperature in °F and °C, and a rest-time range.

⭐

Meta Robots & Canonical Builder

Build a valid meta robots tag and canonical link, or paste existing <head> HTML to audit it for real indexing conflicts like duplicate canonicals and contradictory directives.

• Build mode covers the real documented directive set: index/noindex, follow/nofollow, none, noarchive, nosnippet, noimageindex, notranslate, noyaca, max-snippet, max-image-preview, and max-video-preview.
• Audit mode parses pasted <head> HTML with the browser's own DOMParser and flags multiple canonical tags, contradictory index/follow directives spread across one or more robots meta tags, and non-absolute canonical URLs.
• Self-canonical + noindex detector: flags the classic contradictory case where a page names itself as the canonical version while also telling search engines not to index it.

⭐

Mic Test

Test your microphone online: live level meter, waveform and a record-and-playback check — fully in your browser.

• Microphone picker that refreshes automatically when devices are plugged in or removed.
• Live level meter in dBFS with peak hold, a too quiet / good / too loud verdict and a real-time waveform.
• Record-and-playback check with a downloadable clip, plus per-browser help when access is blocked.

⭐

Random Fake Data & Mock API Generator

Produce realistic mock datasets including names, emails, addresses, companies, and credit cards fully offline.

• Dynamic schema definition mapping names, emails, IDs, and company details.
• Multi-locale localized names synthesis.
• Multiple format database file output builders.

⭐

Morse Code & Cipher Playbook

Translate to Morse code with audio player and decode classic Caesar, Rot13 and Vigenere ciphers.

• Morse translator with sound controls (speed and pitch).
• Caesar cipher shift solver with brute-force text scoring.
• ROT13 and Vigenere cipher support.

⭐

Mortgage Calculator

Calculate your monthly mortgage payment from the home price, down payment, rate and term — with property tax and insurance included.

• Loan amount computed from the home price minus the down payment (percent or amount).
• Monthly principal & interest via the standard annuity formula, term in years or months.
• Optional monthly property tax and home insurance added to the full payment.

⭐

Mouse Sensitivity Converter

Convert mouse sensitivity settings between popular games, calculate eDPI, and find physical cm/360 rotation distance.

• Supports CS2, Valorant, Overwatch, Apex, Fortnite, CoD, and Minecraft
• eDPI and cm/360 or inches/360 calculation
• Visual interactive mousepad simulator

⭐

Mouse Tester

Test every mouse button online: left, right, middle and side buttons light up on a mouse graphic, with press counters, a scroll check and a double-click detector.

• On-screen mouse graphic that lights up left, right, middle, back and forward buttons via mousedown, with per-button press counters.
• Scroll wheel check with separate up and down step counters driven by real wheel events.
• Double-click detector: a log of intervals between consecutive clicks of the same button, flagging gaps under 80 ms as suspected switch bounce.

⭐

Mulch, Topsoil, Compost & Gravel Calculator

Calculate how much mulch, topsoil, compost or gravel you need from area and depth — cubic yards, cubic feet, estimated weight and bags to buy.

• Area from a direct square footage/metreage or from length × width, in feet or metres.
• Depth entered in inches or centimetres, with a hint that a typical mulch layer is 2-4 inches deep.
• Typical bulk density per material (mulch, topsoil, compost, gravel) used for an honest weight estimate, clearly labelled as an estimate.

⭐

Net Present Value (NPV) Calculator

Discount a series of uneven cash flows back to today's value at a chosen rate, with a per-period discounted-value breakdown and a sensitivity table at nearby rates.

• Standard NPV = -initial investment + Σ CF_t / (1+r)^t, computed for up to 10 periods.
• Per-period table of cash flow, discount factor 1/(1+r)^t and present value, summed to the final NPV.
• 5-row sensitivity table recomputing NPV at the entered rate minus 2%, minus 1%, the rate itself, plus 1% and plus 2%.

⭐

Notepad Calculator

Write notes along with mathematical expressions - the tool will calculate everything line by line.

• Line-by-line expression detection.
• Total sum for calculated rows.
• Copy or download the annotated note.

⭐

Number Base Converter

Convert numbers between binary, octal, decimal and hexadecimal — arbitrary size, entirely in your browser.

• Converts between base 2, 8, 10 and 16 in any direction.
• Validates every digit against the source base and points out the offending character.
• Accepts lowercase or uppercase hex digits, spaces and underscore separators.

⭐

OG Image Generator — Social Share Image Maker

Compose a 1200×630 Open Graph social-share image with a title, subtitle, background and logo, rendered live on a real canvas — then preview how it looks framed inside Twitter/X, Facebook, LinkedIn and Discord link cards before you download the clean PNG.

• Solid color, two-color gradient, or an uploaded cover-fit background image
• Title and subtitle with real measureText-based word wrapping and center/left alignment
• Optional corner logo upload plus four honestly-labeled illustrative platform card mockups

⭐

OG & Twitter Card Generator — Meta Tag Builder, Auditor & Preview

Build ready-to-paste Open Graph and Twitter Card <meta> tags from a form, or paste an existing <head> to audit it for missing tags, title/description length and twitter:card validity — then preview both in genuinely re-styled Twitter/X, Facebook, LinkedIn and Discord link-card mockups.

• BUILD mode composes og:title, og:description, og:image, og:url, og:type, og:site_name and matching twitter:card/twitter:site/twitter:title/description/image tags, skipping any field left blank, with a one-click copy of the ready-to-paste block.
• AUDIT mode extracts every og:/twitter: <meta> tag from pasted HTML via the browser's DOMParser, flags missing required tags (og:title/description/image/url), duplicate tags, and invalid twitter:card values.
• Length guidance uses the real commonly-cited thresholds: og:title around 60 characters before some platforms start truncating it (up to roughly 90 on the most permissive), og:description around 155-200 characters.

⭐

One Rep Max (1RM) Calculator

Estimate your one rep max from any set of 2–12 reps using four proven formulas, and get your training percentages from 50% to 95%.

• Epley, Brzycki, Lombardi and O'Conner formulas calculated together with their average.
• Works in kilograms or pounds with any weight, for sets of 2 to 12 reps.
• Training percentage table from 50% to 95% of your estimated max in 5% steps.

⭐

Ovulation Calculator

Estimate your ovulation date, fertile days, and next period from your last period and cycle length.

• Ovulation estimate: cycle length minus 14 days.
• Fertile window: 5 days before ovulation plus the ovulation day.
• Forecast table for the next 3 cycles.

⭐

Paint Calculator — How Much Paint for a Room or Wall

Work out how many liters of paint a room, wall, ceiling or facade needs: wall area from dimensions or direct input, minus doors and windows, times coats — with can sizes to buy.

• Room-dimensions or direct-area input in meters
• Editable coverage (default 11 m² per liter) and coat count
• Can suggestion from 1/2.5/5/10 L sizes and a US-gallon line

⭐

Password Crack Time Estimator

Type a password and see a transparent entropy calculation plus honest crack-time estimates across several clearly-labeled attack scenarios — computed entirely in your browser, never a mystery strength score.

• Live breakdown of detected lowercase, uppercase, digit and symbol character sets and the resulting pool size, recalculated on every keystroke.
• Transparent entropy formula with the exact numbers plugged in, plus a penalty line showing how much weak patterns cost you.
• Crack-time estimates at five illustrative guess rates (online rate-limited, online unthrottled, offline slow hash, offline fast hash on one GPU, offline fast hash on a GPU cluster).

⭐

Password Hasher & Key Derivator

Hash passwords and derive cryptographic keys client-side using PBKDF2 and Scrypt KDF algorithms.

• Compute PBKDF2 (HMAC-SHA256/512) and Scrypt hashes locally.
• Live timing feedback to measure computational hardness.
• Configurable salts and algorithm work factors.

⭐

Payback Period Calculator

Find out how many years or periods it takes for an investment's cash flows to repay its initial cost, with simple and discounted payback compared side by side over a full cumulative cash-flow table.

• Full period-by-period cumulative cash-flow table covering both the simple and discounted variant at once.
• Fractional payback period computed by linear interpolation within the exact period where the balance turns positive.
• Support for uneven, positive or negative cash flows across up to 10 periods, plus an adjustable discount rate.

⭐

Percentage Calculator

Calculate percentages in every direction: X% of a number, what percent X is of Y, percentage change, increase and decrease.

• What is X% of Y, and X is what percent of Y.
• Percentage change between two values with increase/decrease direction.
• Increase or decrease any number by a given percent.

⭐

Permutations & Combinations Calculator (nPr, nCr)

Compute nPr (permutations) and nCr (combinations) from the same n and r, with the real factorial-cancellation working shown step by step in exact BigInt arithmetic.

• nPr and nCr computed from one n and r in a single run.
• Step-by-step descending multiplication chain and, for nCr, the r! division shown explicitly.
• Exact BigInt results for n up to 1000, with very long chains shown in a readable truncated form.

⭐

Position Size Calculator

Enter your account size, risk per trade, entry price and stop-loss to get the exact position size that keeps your risk within your rule, plus an R-multiple profit table.

• Account size, risk % per trade, entry price and stop-loss price drive the core position-size math.
• Results show risk amount, risk per unit, exact and rounded-down position size, position value and % of account, with a leverage warning past 100%.
• Optional target price adds an R-multiple table: 1R, 2R and 3R shown as both a price level and a dollar profit.

⭐

Pregnancy Due Date Calculator

Estimate your due date from the last period, conception date, or IVF transfer, with week-by-week milestones.

• Naegele’s rule with adjustment for cycle length (21–35 days).
• IVF mode for day-3 and day-5 (blastocyst) embryo transfers.
• Key milestone dates: weeks 12, 20, 28, and 37.

⭐

Pressure Converter

Convert pressure units instantly: pascals, kilopascals, megapascals, bar, psi, atmospheres and millimeters of mercury.

• Seven units: Pa, kPa, MPa, bar, psi, atm, mmHg.
• Two-way live fields with one-click unit swap.
• Common-values table that follows your selected units.

⭐

Price per Unit Calculator

Compare 2–4 products by their real unit price: prices are normalized per 100 g, per kg, per litre, per ounce or per item, the cheapest one is highlighted and the rest show how many percent more they cost.

• 2–4 item rows with an optional label, price, quantity and unit (g, kg, ml, l, oz, lb or item).
• Normalized price per 100 g, per kg and per oz for weight, per 100 ml and per litre for volume, per item for counted packs.
• Cheapest item highlighted, the rest tagged with the exact percent difference; one-click copy of the comparison.

⭐

Primality Checker

Test whether a number is prime and see exactly why: real trial division up to √n for small and medium numbers, and a genuine Miller–Rabin walkthrough for cryptography-sized numbers.

• Trial division trace: candidates from 2 up to √n, with the divisor that proves compositeness or the honest '√n checked, no divisor found' proof of primality.
• Deterministic Miller–Rabin with the first 13 prime witnesses (2 through 41) — proven correct below 3,317,044,064,679,887,385,961,981 (≈3.3×10²⁴).
• A real BigInt square-and-multiply modular exponentiation trace, bit by bit, so you can see a(^d) mod n actually being computed.

⭐

Prime Factorization Tree

Factor any integer into its prime factors and see it rendered as the classic branching factor tree taught in school, plus the compact exponent form (360 = 2³ × 3² × 5).

• Visual SVG factor tree, with prime leaves and still-splittable branches shown differently.
• Exact trial-division factorization using BigInt, supporting integers up to 1,000,000,000,000.
• Compact exponent-form result computed by tallying the tree's prime leaves.

⭐

Projectile Motion Calculator

Enter a launch speed and angle to get the real range, max height and time of flight of a projectile — the launch velocity is decomposed into vx and vy, every kinematics substitution is shown, and an actual trajectory chart is plotted from those same equations.

• Inputs for launch speed, launch angle (0–90°) and an optional launch height, with a metric/imperial unit toggle that swaps the gravitational constant used.
• Computes time of flight, maximum height and range with every substitution step written out, including the quadratic formula used for elevated launches.
• Plots the parabolic trajectory as an SVG chart sampled directly from the position equations, with gridlines, axis labels and the apex and landing points marked.

⭐

Protein Intake Calculator (Daily Range)

Get your daily protein target as an honest low-high range in grams, based on your body weight and activity goal — plus food equivalents, right in your browser.

• Body weight in kg or lb with five activity/goal presets from sedentary to endurance training
• Daily protein range in grams, plus the g-per-kg formula shown in full
• Food equivalents table (chicken breast, eggs, Greek yogurt) based on the midpoint of your range

⭐

PX to REM Converter

Convert px to rem, rem to px and px to em at any base font size, with a copy-ready CSS line and a live reference table.

• Three directions in one selector: px → rem, rem → px and px → em.
• Adjustable base font size (16px by default) applied to the result and every table row.
• Reference table for common sizes from 1 to 64 px, recalculated for the current base with the base row highlighted.

⭐

Pythagorean Theorem Calculator

Solve a² + b² = c² step by step: find the hypotenuse from two legs, find a missing leg, or test whether three sides form a right triangle — with exact simplified radicals like 5√2, a scaled diagram, area and perimeter.

• Three modes: find the hypotenuse from two legs, find a missing leg from a leg and the hypotenuse, and check whether three sides make a right triangle.
• Exact arithmetic on decimal inputs and exact simplified radicals (c = 5√2) next to rounded decimals.
• Also computes the area and perimeter of the triangle and draws it with the right angle marked.

⭐

QR Code Generator

Create custom QR codes from links, texts and Wi-Fi networks locally in the browser.

• Download high-resolution image outputs.
• Supports text URLs, emails, and Wi-Fi configurations.

⭐

QR Code Scanner

Scan QR codes from files or your webcam instantly and privately in your browser.

• Supports Webcam scanner reading.
• Supports local file upload decoding.

⭐

Quadratic Equation Solver

Solve ax² + bx + c = 0 with the full quadratic formula worked out step by step: exact roots like (3 ± √5)/2 or −1 ± 2i, the discriminant, the vertex and the factored form.

• Handles all three cases: two real roots, one repeated root and complex conjugate roots.
• Simplifies radicals (√48 → 4√3) and cancels common factors with 2a for the cleanest exact form.
• Also reports the vertex (−b/2a, −D/4a) with the vertex form and factors the trinomial when the roots are rational.

⭐

Race Training Plan Generator

Build a safe week-by-week mileage progression for your next race from your current mileage, race distance and weeks to go, using the published 10% rule plus a step-back taper.

• Week-by-week mileage table labeled building, recovery or taper, generated from a real iterative simulation, not a straight-line ramp.
• Distance-aware peak-mileage guidance blended with your current weekly mileage, not a one-size-fits-all target.
• Honest "not enough time" detection when even a strict 10%-per-week build can't reach a safe mileage base for your goal.

⭐

Ratio Calculator

Simplify ratios, solve proportions A : B = C : x, scale ratios by any factor and convert them to fractions, decimals and percentages — with every step shown.

• Four modes: simplify a ratio, solve a proportion, scale by a factor, and convert a ratio.
• Decimal inputs are handled exactly by scaling both sides to whole numbers first.
• Converts any ratio to a simplified fraction, a decimal and a percentage at once.

⭐

Recipe Scaler

Paste an ingredient list, set the original and the target number of servings, and get every quantity rescaled with kitchen-friendly rounding.

• One ingredient per line; the scaled list keeps your original wording and only replaces the leading quantity.
• Any factor via servings: 4 → 6 servings multiplies by 1.5, and presets cover halving, doubling and tripling.
• Quarter-fraction output (¼, ½, ¾) for cups, tablespoons and teaspoons; numeric rounding for g, kg, ml and l.

⭐

Refresh Rate Test

Measure the refresh rate your browser really renders: a live Hz readout from frame timestamps, a frame-time graph, a skipped-frame counter and a UFO-style smoothness test.

• Live Hz readout computed as the median of the last 60 requestAnimationFrame intervals.
• UFO-style motion strips at full, half and quarter of the measured rate with an adjustable speed slider.
• Frame-time graph with slow frames highlighted and a running skipped-frame counter.

⭐

Regex Tester Online

Debug JavaScript regular expressions live: highlighted matches, capture groups, flags, and replacement preview.

• Live match highlighting with a match counter
• Full flag control: g, i, m, s, u
• Replacement mode with $1, $& and $<name> references

⭐

Rent Affordability Calculator

See how much rent you can afford under three real published affordability rules side by side — the 30% rule, the 50/30/20 budget, and the landlord's 40x-rent screening rule — plus a reverse mode that turns a target rent into a required income.

• 30% rule: maxRent = 30% of monthly income, the classic HUD-cited affordability guideline.
• 50/30/20 budget rule shown as an honest range (~25% to ~50% of income) since rent shares the 'needs' bucket with other expenses.
• 40x rent rule: the common landlord/leasing-office screening threshold, annual income ÷ 40.

⭐

Ring Size Converter

Convert ring sizes between the US, UK, EU/ISO and Japanese systems, or start from a measured diameter or circumference in millimetres.

• ISO 8653 based conversion table with 44 standard sizes.
• Accepts UK letter sizes including halves, like M or M½.
• Millimetre inputs are interpolated between table rows for an exact match.

⭐

ROI Calculator

Calculate the return on any investment: total ROI %, profit, annualized CAGR and the doubling time by the rule of 72 next to the exact answer.

• Total ROI % = (final − initial) / initial, plus the absolute profit or loss.
• Annualized CAGR = (final/initial)^(1/years) − 1 whenever you enter the holding period, fractional years included.
• Doubling time two ways: the rule-of-72 estimate (72 / rate) side by side with the exact ln 2 / ln(1 + r).

⭐

Roman Numerals Converter

Convert numbers 1–3999 to Roman numerals and back, with a place-by-place breakdown and strict validation.

• Bidirectional conversion for 1–3999
• Place-value breakdown of every result
• Strict validation of Roman numeral syntax

⭐

Roofing Shingle Calculator — Squares & Bundles from Pitch

Add up your roof's footprint sections, enter the pitch as rise per 12 inches of run, and get the real sloped roof area, plus the squares and bundles of shingles to buy after waste — using the actual trigonometric pitch factor roofers use, not a flat area estimate.

• Repeatable roof-section rows: length × width or a direct footprint area per row, add or remove freely
• Real pitch-factor trigonometry (sqrt(rise² + 12²) ÷ 12) converting flat footprint to actual sloped area
• Results in real trade units — squares and bundles — with adjustable waste % and bundles-per-square

⭐

Rounding Calculator

Round any number to any place value — from millions to ten-thousandths — with exact digit-by-digit math and a clear explanation of the result.

• Eleven place values: million, hundred thousand, ten thousand, thousand, hundred, ten, whole number, tenth, hundredth, thousandth and ten-thousandth.
• Four rounding modes: half up (school standard), half even (banker's), floor and ceiling.
• Digit-based math on the number you typed, immune to binary floating-point artifacts.

⭐

Running Pace Calculator

Calculate your running pace per km and per mile, finish time and km splits, or predict race times with the Riegel formula — right in your browser.

• Pace mode: distance + time gives pace per km, pace per mile, speed and km splits
• Time mode: distance + target pace gives your projected finish time
• Predictor mode: one known race result forecasts 5K, 10K, half and marathon times with Riegel's T2 = T1 × (D2/D1)^1.06

⭐

Salary Converter

Convert any pay amount between hourly, daily, weekly, biweekly, monthly and annual — based on your real hours per week and weeks per year.

• One input converted into all six pay periods: hour, day, week, two weeks, month and year.
• Adjustable hours per week (default 40) and paid weeks per year (default 52), including decimals.
• Shows how many of each period fit into a year, so every conversion is easy to verify.

⭐

Savings Goal Calculator

Plan a savings goal two ways: find the monthly deposit that reaches a target amount by a date, or how long a given monthly deposit will take, with interest.

• Monthly-deposit mode: goal amount, horizon in years or a deadline date, current savings and annual rate in — required monthly deposit out.
• Time-to-goal mode: solves the same compound-growth relation for the number of months with logarithms, then shows the projected final balance.
• Zero-interest edge handled exactly: with a 0% rate the answer collapses to simple division, e.g. 12,000 in one year means 1,000 per month.

⭐

Schema Markup Generator (JSON-LD)

Build valid JSON-LD structured data for FAQ, Article, Local Business, Product, Breadcrumb, Organization and Event pages — live, private, ready to paste.

• Seven schema types: FAQPage, Article, LocalBusiness, Product, BreadcrumbList, Organization and Event, each with its own field set.
• Repeatable rows for FAQ question–answer pairs and breadcrumb items, with add and remove buttons.
• One-click copy of the finished <script type="application/ld+json"> block, safely escaped for embedding in HTML.

⭐

Screen Resolution Checker

See your screen resolution, browser viewport size, device pixel ratio, color depth and orientation — updated live as you resize.

• Screen resolution, browser viewport size, device pixel ratio with physical pixel math, color depth and orientation.
• Values refresh automatically on window resize and orientation change.
• Everything is read locally from browser APIs — nothing is sent to a server.

⭐

Developer Secrets & Token Generator

Bulk generate cryptographically secure API keys, salts, tokens, and decode precise millisecond timestamps from UUIDv7.

• Bulk generation of UUIDv4, UUIDv7, Hex salts, and Base64 tokens.
• Timestamp decoder for UUIDv7 identifiers.
• Environment and configuration syntax builders.

⭐

Security Headers Analyzer

Paste raw HTTP response headers from curl -I or DevTools' Network tab and get a graded security audit — a real Content-Security-Policy grammar parser plus HSTS, X-Frame-Options, cookie flags and more, entirely offline.

• Checks Content-Security-Policy (full directive-by-directive lint), Strict-Transport-Security (max-age, includeSubDomains, preload), X-Content-Type-Options, X-Frame-Options (aware of the modern CSP frame-ancestors equivalent), Referrer-Policy, Permissions-Policy and Set-Cookie flags (Secure/HttpOnly/SameSite).
• Every finding expands into the exact reason it was flagged — for CSP that means naming the specific directive and the specific unsafe token or wildcard found in it, not a generic warning.
• One-click copy of a plain-text report summarizing the grade and every finding, ready to paste into a ticket, pull request or security review.

⭐

SERP Snippet Preview

See how your title tag and meta description will look in Google search results — live desktop and mobile snippet preview with character and pixel counters.

• Desktop and mobile preview modes with device-specific pixel limits (~600 px title / ~960 px description on desktop).
• Dual counters for both fields: characters against the 60/160 guidelines and pixels against the device limit, turning red when exceeded.
• Google-style snippet mock with favicon placeholder, breadcrumb URL path and … truncation exactly where the text overflows.

⭐

Shoe Size Converter

Convert shoe sizes between US, UK, EU, JP and foot length in cm for men, women and kids — with the full chart row for every match.

• Five sizing systems: US, UK, EU, JP and mondopoint foot length in centimetres.
• Measured foot length in cm is interpolated to the nearest chart size.
• Kids' chart covers both child (C) and youth (Y) US sizes.

⭐

Sig Fig Calculator

Count the significant figures in any number with every digit classified by rule, or round a number to 1–15 significant figures with exact string-based math.

• Counter mode: per-digit classification — nonzero, captive zero, leading zero, trailing zero with or without a decimal point.
• Rounding mode: 1 to 15 significant figures with digit-string math, so 0.0019997 becomes 0.00200 with its trailing zeros intact.
• Optional scientific notation output, like 1.20 × 10³.

⭐

Sleep Calculator — Sleep Cycle Bedtime & Wake-up Times

Find the best time to go to bed or wake up based on 90-minute sleep cycles, with age-based sleep recommendations — right in your browser.

• Six suggested times labeled with cycle count and hours of sleep
• Accounts for the average 15 minutes needed to fall asleep
• Recommended options highlighted for your age group

⭐

Slope Calculator

Find the slope between two points as an exact fraction, plus the y-intercept, slope-intercept and point-slope forms, distance with a simplified radical, midpoint and angle of incline — with steps.

• Exact fraction arithmetic — decimal coordinates like 2.5 are stored as exact fractions, never rounded.
• Vertical lines are reported honestly: undefined slope with the line equation x = c instead of a fake huge number.
• Distance between the points is simplified as a radical (√45 → 3√5) with the decimal value next to it.

⭐

Speaker Test

Test your speakers online: left / right channel tones, a 20–200 Hz bass sweep and pink noise — all generated in your browser.

• Left / Right / Both channel buttons routed through a StereoPannerNode, with a visual indicator of which channel is playing.
• Bass sweep that glides from 20 to 200 Hz over 8 seconds, plus locally generated pink noise for balance and placement checks.
• Frequency slider from 100 to 2000 Hz that retunes the test tone live while it plays.

⭐

Speed Converter

Convert speed units instantly: meters per second, km/h, mph, knots and feet per second.

• Five units: m/s, km/h, mph, knots, ft/s.
• Two-way live fields with instant swap.
• Common-values table with driving, sailing and physics speeds.

⭐

SQL Formatter

Format and beautify SQL queries or minify them to one line — entirely in your browser.

• Uppercases SQL keywords (SELECT, FROM, JOIN, WHERE…) while leaving strings, comments and quoted identifiers untouched.
• Indents subqueries and breaks SELECT column lists, JOINs and AND/OR conditions onto separate lines with 2- or 4-space indentation.
• Minify mode collapses a whole query to one clean line and strips comments.

⭐

SRI Hash Generator

Generate a Subresource Integrity hash for any JS or CSS file and get a ready-to-paste script or link tag.

• Compute sha256, sha384 or sha512 digests of a dropped file locally.
• Base64-encode the digest into a correct integrity="sha384-..." value.
• Generate a complete, editable <script> or <link rel="stylesheet"> snippet.

⭐

Stair Calculator — Risers, Tread Depth & Blondel Comfort Check

Plan a staircase from total floor-to-floor rise: get the number of risers, the exact riser height, a tread depth from the real Blondel comfort formula (2 x riser + tread), and whether the total run fits your available space.

• Riser count from ceil(total rise / max riser height), with the exact resulting riser height shown (usually a little under your chosen maximum)
• Tread depth solved from the real Blondel formula (2R + T in the ~24-25 in comfort band), clamped up to your minimum tread when the two disagree — and flagged when that happens
• Adjustable max riser height (default 7.75 in / 196.85 mm) and min tread depth (default 10 in / 254 mm), based on common IRC residential limits but editable since exact code varies by jurisdiction

⭐

Standard Deviation Calculator

Paste your numbers and get the sample or population standard deviation, variance, mean, SEM and CV% — with the squared deviations shown step by step.

• Standard deviation, variance, mean, standard error of the mean (SEM) and coefficient of variation (CV%).
• Exact two-pass algorithm: the mean first, then the true squared deviations — no streaming shortcuts.
• Step-by-step deviations table (first 50 rows for long lists, with sums always covering every value).

⭐

Startup Cost Calculator

Add your one-time and monthly recurring costs, set a runway in months and a contingency buffer, and see the total capital you need to launch and survive.

• Repeatable one-time and monthly recurring cost rows — add or remove as many as you need, each with its own label and amount.
• Adjustable runway length in months and a contingency percentage layered on top of the base total.
• Visual one-time vs. recurring breakdown plus a marginal-value readout: how many extra months an additional 1,000 in funding buys.

⭐

Steps to KM Calculator — Steps, Distance, Miles & Calories

Convert steps to kilometers and miles (or find out how many steps a distance takes), using your real stride length or one estimated from your height, plus an optional walking calorie estimate.

• Steps → distance mode: distance shown in kilometers and miles at once, from any step count up to a million
• Distance → steps mode: type a distance in km or miles and get the steps needed at your stride length
• Optional calorie estimate (3.5 METs walking) once a body weight is entered, alongside the stride length actually used

⭐

String Escaper — JSON, JS, SQL & Regex

Escape or unescape strings for JSON, JavaScript/TypeScript, SQL and regex — live, entirely in your browser.

• Live conversion on every keystroke — no button to press.
• JavaScript mode lets you pick single quotes, double quotes or backticks, and escapes exactly what that quote style needs, including template-literal ${.
• Clear, localized error messages when a malformed escape sequence can't be decoded, instead of a crash or a blank result.

⭐

Subnet Calculator

Calculate the network address, broadcast, subnet and wildcard masks, host range and usable host count for any IPv4 address and CIDR prefix.

• Network address, broadcast address, subnet mask and wildcard mask for any IPv4/CIDR pair.
• First and last usable host plus usable-host and total-address counts (2^(32−p) − 2 arithmetic).
• IP class note for the entered address and a one-click copy of the full result summary.

⭐

Subtitle Converter

Convert subtitles between SRT and VTT, shift their timing by milliseconds or seconds, and renumber cues — privately in your browser.

• Convert SRT to WebVTT and WebVTT to SRT with correct timestamp separators and sequential renumbering.
• Shift all timestamps forward or backward by milliseconds or seconds; negative results are clamped at 00:00.
• Load a .srt or .vtt file or paste subtitle text, then download the result with the right extension.

⭐

Random Team Generator

Paste a list of names and split it into fair random teams by team count or group size.

• Split by number of teams or by people per team
• Optional automatic team names
• One-click copy of the result

⭐

Temperature Converter

Convert temperatures between Celsius, Fahrenheit and Kelvin instantly with exact formulas.

• Three scales: Celsius, Fahrenheit and Kelvin.
• Two-way live fields with the exact formula displayed.
• Reference table of everyday temperatures: weather, body, cooking, boiling.

⭐

Test Card Number Generator (Luhn-Valid, Sandbox Only)

Generate fake, Luhn-checksum-valid test card numbers from publicly documented sandbox BIN ranges (Visa, Mastercard, Amex, Discover) for QA and checkout-flow testing. Not real cards.

• Real Luhn algorithm implemented from scratch: from the rightmost digit, double every second digit, subtract 9 from any result over 9, sum everything, and solve for the check digit that makes the total a multiple of 10.
• Test BIN prefixes drawn from widely documented sandbox test numbers (the same 424242, 411111, 555555, 510510, 378282, 371449, 378734, 601111 and 601100 style prefixes published by major payment gateways for developers testing checkout integrations) - the middle digits are freshly randomized behind each prefix.
• Per-network formatting and field lengths: 16-digit numbers grouped 4-4-4-4 for Visa/Mastercard/Discover, 15-digit Amex grouped 4-6-5, 3-digit CVV for most networks and 4-digit CVV for Amex.

⭐

Text Similarity Checker

Compare two texts with real n-gram Jaccard similarity and a word-level LCS overlap score, with the matching passages highlighted side by side.

• N-gram Jaccard index: tokenizes both texts into word n-grams and computes |intersection| / |union| of the two n-gram sets.
• Word-level Longest Common Subsequence via a real dynamic-programming table, backtracked to recover exactly which words matched.
• Side-by-side highlighted rendering maps every LCS-matched word back onto the original text, preserving its spacing and punctuation.

⭐

Tile Calculator — How Many Tiles You Need

Work out how many tiles a floor, wall or laminate installation needs: enter a room's dimensions or its area directly, pick a common tile size or a custom one, add a waste allowance for cuts, and get a shopping list in tiles and boxes.

• Direct-area or length × width input in feet or meters
• Six common tile sizes plus a custom width/height option
• 10% / 15% waste presets with the diagonal-lay explanation

⭐

Tip Calculator

Calculate the tip and total for any bill, and split both evenly between any number of people.

• Tip amount and grand total from the bill and tip percent.
• Even split between any number of people, tip included.
• Any tip percent, including decimals like 12.5%.

⭐

Tire Size Calculator — Diameter & Speedometer Error Comparison

Parse metric (225/45R17) or flotation (33x12.5R15) tire codes, get sidewall height, overall diameter, circumference and revolutions per mile/km, and compare two sizes with the resulting speedometer error.

• Sidewall height, overall diameter and circumference for each tire, shown in millimeters and inches
• Revolutions per mile and per kilometer, plus wheel RPM at a reference speed you choose
• To-scale side-by-side diagram of the two tires and their rims, and a signed diameter difference in inches and percent

⭐

Table of Contents Generator

Paste Markdown or HTML and get a nested, clickable table of contents with real GitHub-style collision-safe anchor slugs, plus the original content with heading IDs injected.

• A genuine line-by-line Markdown parser that tracks fenced code-block state, so headings are only recognized outside ``` and ~~~ fences - not a naive regex over the whole text.
• A real occurrence-counting slug engine: every slug is tracked in a map as it's assigned, and a repeat gets the next free -1, -2, -3 suffix in order of appearance, exactly like GitHub's own anchor algorithm.
• Two content-output modes: Markdown with the widely-supported {#slug} heading-attribute syntax (kramdown, Pandoc, MkDocs, Jekyll/GitHub Pages), or HTML with real id="slug" attributes injected into the heading tags for renderers that don't support the attribute syntax.

⭐

TOTP Generator — Live 2FA Authenticator Code

Paste a Base32 TOTP secret and watch the real, live 6-digit authenticator code rotate every 30 seconds — entirely offline in your browser.

• Live 6- or 8-digit code that recomputes every second from the current Unix time counter.
• Circular countdown ring showing exactly how many seconds remain in the current time step.
• One-click code copy plus support for SHA-1, SHA-256 and SHA-512 and a configurable period.

⭐

Triangle Calculator

Solve any triangle from three known values — SSS, SAS, ASA, AAS or SSA — and get every side, every angle, the area, the perimeter and the heights, with the law of sines and cosines steps written out and a scaled diagram.

• Five input cases: three sides (SSS), two sides + included angle (SAS), two angles + included side (ASA), two angles + non-included side (AAS), two sides + non-included angle (SSA).
• Computes all sides, all angles in degrees, the area (Heron's formula for SSS, ½·a·b·sin C otherwise), the perimeter and all three heights.
• Inline SVG diagram scaled to the solved triangle with labeled vertices, sides and a right-angle marker.

⭐

Tweet Thread Splitter

Paste a long post and split it into a real X/Twitter thread using the actual weighted character-counting rules — every URL counts as a fixed 23 characters and astral-plane emoji count correctly — with smart paragraph/sentence/word boundaries and thread numbering that reserves its own space.

• Real weighted character counting: iterates actual Unicode code points (so a surrogate-pair emoji counts once, not twice) and applies the same weighted-range table X's own twitter-text library uses — most Latin/common-script characters weigh 1, everything else (CJK, most emoji, symbols) weighs 2.
• Every URL-like substring is detected and counted as a fixed 23 characters, matching the real t.co link-shortening behavior, regardless of the URL's actual literal length.
• A three-tier smart splitter: paragraphs first, then sentences (regex-based boundary detection with guards against abbreviations and decimal points), then individual words as a last resort, so text is never torn mid-word or mid-link.

⭐

URL Parser & Query Inspector

Deconstruct complex URLs, manage deep queries, and decode URL parameters cleanly fully client-side.

• URL parsing into component segments (protocol, domain, path, query).
• Live JSON code formatting for nested JSON parameters.
• Interactive parameter grid and path rebuilder.

⭐

User Agent Parser

Paste any user-agent string — from a server log, a support ticket, or curiosity — and decode its browser, OS, engine and device type instantly, including known bots like Googlebot.

• Live parsing as you type or paste, with no submit button: browser name and version, operating system, rendering engine and device type (desktop, mobile, tablet or bot) update on every keystroke.
• Explicit known-bot detection with a plain yes/no flag plus the matched bot's name — Googlebot, Bingbot, facebookexternalhit, Twitterbot, AhrefsBot, SemrushBot and more.
• A 'load my own current browser's UA' button fills the box with your real navigator.userAgent as a quick way to try the parser, though the core use case is pasting any arbitrary string.

⭐

UTM Link Builder

Build campaign URLs with utm_source, utm_medium and utm_campaign tags — live output, validation and clean encoding in your browser.

• All five parameters: utm_source, utm_medium, utm_campaign, utm_term, utm_content
• Lowercase and spaces-to-dashes toggles for consistent tag hygiene
• One-click copy plus a local history of the last five links

⭐

VAT Calculator

Add VAT to a net price or extract it from a gross price at any rate — net, VAT amount and gross in one click.

• Net price, VAT amount and gross price from a single input.
• Add mode (net → gross) and remove mode (gross → net) with the exact division formula.
• One-click copy of the full breakdown.

⭐

vCard Generator (VCF)

Create a vCard 3.0 contact file (.vcf) with a live preview and a QR code that adds the contact to any phone on scan — free, in your browser.

• Full contact form: first and last name, organization, job title, mobile and work phones, email, website, address and a free-text note.
• One-click .vcf download named after the contact, ready for import into iOS, Android, Google Contacts and Outlook.
• Optional QR code carrying the complete vCard payload, with a density warning when the contact grows past QR-friendly size.

⭐

Vector Calculator

Compute the dot product, cross product, magnitude, unit vector and angle between two 2D or 3D vectors — with the term-by-term dot product expansion, the i/j/k determinant mnemonic, and exact simplified radicals like 5√2 shown at every step.

• Dot product, cross product (3D), magnitude, unit vector and the angle between two vectors in one run, with a dimension toggle for 2D or 3D.
• Exact arithmetic on decimal components and exact simplified radicals for magnitudes and unit vectors, next to rounded decimals.
• The angle between the vectors is reported with the arccos formula plugged in, in both degrees and radians.

⭐

Video Trimmer — Cut Video Online

Trim a video to the exact segment you need directly in your browser — sliders with frame preview, no upload, no watermark.

• Start/end sliders with live frame preview and a thumbnail filmstrip.
• Real-time capture through captureStream() and MediaRecorder.
• Codec picker built from MediaRecorder.isTypeSupported() results.

⭐

VO2 Max Calculator

Estimate your VO2 max (cardiorespiratory fitness) from the Cooper 12-minute run or the Rockport 1-mile walk test, with a fitness-level category by age and sex.

• Cooper 12-Minute Run Test: enter the distance covered in meters or miles for the published (distance − 504.9) / 44.73 formula.
• Rockport 1-Mile Walk Test: enter walk time, end-of-walk heart rate, weight and age for the Kline et al. five-variable regression.
• Fitness-category lookup across five age bands (20s through 60+) and both sexes, with the exact range shown for your group.

⭐

Volume Converter

Convert volume units instantly: milliliters, liters, teaspoons, tablespoons, fluid ounces, cups, pints, quarts, gallons and cubic meters.

• Ten units: ml, liters, teaspoons, tablespoons, fluid ounces, cups, pints, quarts, gallons and cubic meters.
• Two-way live fields with one-click unit swap.
• Common-values table that follows your selected units.

⭐

Waist-to-Hip Ratio Calculator

Calculate your Waist-to-Hip Ratio (WHR) from waist and hip circumference, with the WHO 2008 risk category and a separate NIH/ATP-III waist-circumference cross-check.

• WHR = waist ÷ hip, compared against the sex-specific WHO 2008 threshold (0.90 for men, 0.85 for women).
• Separate NIH/ATP-III panel comparing your waist circumference alone against its own sex-specific cutoff (102 cm / 40 in for men, 88 cm / 35 in for women).
• Unit toggle between centimeters and inches, with sanity-checked input ranges for each.

⭐

Wallpaper Calculator — Rolls Needed, Pattern-Repeat Waste Included

Work out how many wallpaper rolls a room needs: enter the wall length (or room length × width) and height, pick a roll size, and — unlike a flat waste percentage — enter the pattern repeat so the calculator can show the real material lost to matching a large repeat.

• Room perimeter or direct wall-length input, with an optional opening-width deduction
• Standard metric roll, US double roll, or fully custom width and length
• Pattern-repeat-aware strip rounding with a transparent waste percentage

⭐

WASM Disassembler & Demangler

Decompile WebAssembly binary modules into readable WAT S-expressions and demangle compiler function symbols client-side.

• WebAssembly binary section parser and visual dashboard.
• WAT S-expression disassembler.
• Mangled C++ and Rust symbol translator.

⭐

Water Intake Calculator

Estimate how much water you should drink a day from your weight, exercise and climate — in liters, milliliters and 250 ml glasses, right in your browser.

• Baseline of ~35 ml per kg of body weight
• Exercise adjustment (+350 ml per 30 minutes) and hot-climate bump (+500 ml)
• Transparent breakdown showing how the total was built

⭐

Webcam Test

Check your webcam online: live preview, real resolution and frame rate readout, and a PNG snapshot — fully in your browser.

• Camera picker that refreshes automatically when devices are plugged in or removed.
• Mirrored live preview with a mirror toggle and live readout of camera name, resolution and frame rate.
• Un-mirrored PNG snapshot download, plus per-browser help when camera access is blocked.

⭐

Weight Converter

Convert weight and mass units instantly: milligrams, grams, kilograms, tonnes, ounces, pounds and stone.

• Seven units: mg, g, kg, tonnes, ounces, pounds, stone.
• Two-way live fields with instant unit swap.
• Common-values table tuned to the selected units (body weight, cooking amounts).

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What Is My Browser

See your browser name and version, operating system, rendering engine and full user agent string the moment the page loads — detected locally.

• Browser name and version, operating system and rendering engine via navigator.userAgentData with a user-agent string fallback.
• Full user agent string in a copyable field, plus browser language, cookie status, viewport size, device pixel ratio and touch support.
• Honest detection: whatever the browser does not reveal is reported as Unknown instead of being guessed.

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Wheel Spinner

Spin a weighted decision wheel locally in your browser.

• One option per line with optional weights
• Animated SVG wheel with colored sectors
• Winner result copied from a simple text output

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Z-Score & Confidence Interval Calculator

Compute a z-score for a value against a normal distribution, or a confidence interval for a sample mean — with the standardization formula and the exact critical z-value substituted step by step.

• Z-score mode: z = (x − μ) / σ plus the cumulative probability Φ(z), and the one-tailed and two-tailed tail areas from an Abramowitz & Stegun standard-normal CDF approximation.
• Confidence interval mode: margin of error z × (σ / √n) and the interval x̄ ± margin, fully substituted, for 80/90/95/98/99% confidence.
• A dynamic form that only shows the inputs the selected mode needs, and reads locale decimal-comma numbers like 3,14 correctly.

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ZIP Creator — Make a ZIP Archive Online

Pack any files into a single ZIP archive with your chosen compression level, entirely in the browser.

• Multi-file upload with drag & drop, folder structure preserved via relative names.
• Compression level select: 0 (store), 6 (default), 9 (maximum).
• Shows the compression ratio achieved after the archive is created.

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ZIP Extractor — Open ZIP Files Online

Open any ZIP archive in your browser: browse the full file tree with sizes and download only the files you need — nothing is uploaded.

• File tree with collapsed folders, per-file sizes and total statistics.
• One-click download of any single file, or all files one by one.
• Reads standard ZIP archives from any operating system or tool.