Useful utilities | Invistools

Utilities cover the jobs that are not a file type of their own: format JSON, build a QR code, convert a unit, or work out a loan payment. Open the tool whose name is the job.

A Wi-Fi QR, a Markdown draft, or a percentage of a price are three different tools. The list below is the catalogue; it is not one combined app.

A calculator result is the formula on the page, not a bank, tax or medical decision. A very large paste is limited by the memory of the tab.

Utilities in this category

35 tools

⭐

Base64 / Hex / Binary Multi-Coder

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

Use this tool when Do you need to convert binary files like images or PDFs into Base64 strings for web embedding?

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

Evaluate one arithmetic expression with parentheses, powers, percent, and the listed functions, in degrees or radians.

Use this tool when Do you need to quickly check the amount of expenses or calculate a discount in the store?

Operators + − * / % and ^, plus parentheses
abs, sqrt, sin, cos, tan, ln, log, round, floor, ceil, min, max
Constants pi and e, and a degree or radian switch

⭐

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.

Use this tool when Never measured your bra size before and want a solid starting point before you shop?

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.

⭐

Clothing Size Converter

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

Use this tool when Ordering a dress from a European store and only know your US size?

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.

Use this tool when Do you need to quickly structure chaotic HTML or CSS code before adding it to your site?

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.

⭐

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.

Use this tool when Order the right number of pre-mixed bags for a shed slab or patio before a trip to the hardware store.

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

⭐

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.

Use this tool when Get the exact CSS to center a div both horizontally and vertically by watching justify-content and align-items work on live preview boxes.

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.

⭐

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.

Use this tool when Check a second-hand controller before paying: press every button and pull both triggers to see their fractional values respond.

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.

⭐

Cryptographic Checksum Hash Generator

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

Use this tool when Do you need to compute MD5, SHA-1, SHA-256 or SHA-512 hashes for text or binary 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.

⭐

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.

Use this tool when Turn a quick list of stats you're citing in a blog post into a clean HTML table by typing straight into the grid, without hand-writing a single <td>.

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.

⭐

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.

Use this tool when Spot exactly what a backend change broke by pasting yesterday's API response as Original and today's as Changed, instead of eyeballing two walls of formatted JSON.

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.

Use this tool when Do you need to make a server response that comes in compressed JSON readable?

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.

⭐

JWT Token Debugger

Decode a JWT header and payload, and compare the signature with HMAC-SHA256 of the secret you type.

Use this tool when Do you need to decode, inspect and verify the signature of JWT tokens client-side?

Three segments required
No alg switch: the check is HMAC-SHA256 even if the header says otherwise
Rebuild writes a new HMAC token from the edited JSON

⭐

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.

Use this tool when Check every key of a second-hand or repaired keyboard: walk across the rows and any key that never lights up is dead.

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.

⭐

Magic Bytes & Binary Header Doctor

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

Use this tool when Do you want to identify the true file type of a document using magic byte signatures?

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

⭐

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.

Use this tool when Work out how long to roast this year's Thanksgiving turkey from its weight, with the USDA-safe 165°F pull temperature and a 20-30 minute rest before carving.

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.

⭐

Random Fake Data & Mock API Generator

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

Use this tool when Do you want to produce realistic mock datasets with names, emails, and phone numbers 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

Encode and decode Morse, plus a Caesar shift, ROT13, and a Vigenère shift, with a tone for the Morse you just encoded.

Use this tool when Do you need to translate text to Morse code and play it using Web Audio frequencies?

Morse, Caesar, ROT13, and Vigenère
Dot length is 1.2 divided by the WPM box, which opens at 20
Unknown Morse characters are dropped on encode and become ? on decode

⭐

Mouse Sensitivity Converter

Convert sensitivity with a fixed yaw per game, and read eDPI and centimeters per 360 degree turn.

Use this tool when Switching from Counter-Strike to Valorant or Apex and want to keep your exact muscle memory aim?

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.

Use this tool when Prove a suspected hardware double-click: single-click repeatedly and look for flagged intervals under 80 ms in the log.

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.

⭐

Notepad Calculator

Keep notes and math on the same page. Lines with an expression are evaluated, and the results are totaled.

Use this tool when Do you need to make a detailed estimate or calculate your monthly expenses?

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

⭐

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%.

Use this tool when Estimate your bench, squat or deadlift max safely from a heavy set of five instead of a risky max-out attempt.

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.

⭐

QR Code Generator

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

Use this tool when Need to share links via QR codes?

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

⭐

QR Code Scanner

Decode a QR code from a photo or the camera with jsQR, and copy the text it contains.

Use this tool when Need to decode a QR code from a screenshot sent in Messenger?

Camera scan with jsQR about five times a second, and image decode from a file
Plain-text result you copy yourself. Barcodes are ignored.

⭐

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.

Use this tool when Verify a new 120, 144 or 240 Hz monitor is actually running at its advertised rate and not the 60 Hz the operating system defaulted to.

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.

⭐

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.

Use this tool when Check math homework: see not just the rounded answer but the digit and rule that produced it.

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.

⭐

SQL Formatter

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

Use this tool when Beautify a long production query before a code review so every column, JOIN and WHERE condition is visible at a glance.

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.

⭐

Subtitle Converter

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

Use this tool when Convert a downloaded .srt file to WebVTT so the captions finally load in an HTML5 video player or on a web platform that only accepts .vtt.

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.

⭐

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.

Use this tool when Cut the useful part out of a long screen recording before sharing it with colleagues.

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.

⭐

WASM Section Inspector and Demangler

List the sections inside a .wasm binary and turn Itanium _ZN symbol names into namespace paths, in the browser.

Use this tool when Do you want to decompile compiled binary WebAssembly files into readable WAT S-expressions?

WebAssembly section list with sizes and a bar scaled to 4 KB.
Itanium demangler for lines that start with _ZN.
Local FileReader parse of a .wasm binary.

⭐

Webcam Test

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

Use this tool when Check your framing, lighting and camera before joining an online interview or important video meeting.

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.

Use this tool when Convert body weight between kilograms, pounds and stone for foreign forms and fitness apps.

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).

⭐

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.

Use this tool when Answer the support question "what browser and version are you on?" in one glance.

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.

⭐

Wheel Spinner

Spin a wheel whose slice sizes follow the weights you type, and read the label under the top pointer when it stops.

Use this tool when Do you need one visual way to choose between several options?

One entry per line, with an optional colon and weight
SVG slices from a fixed palette of eight colors
One winner, written when the spin speed falls to 0.05

⭐

ZIP Creator — Make a ZIP Archive Online

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

Use this tool when Need to email a folder of documents as a single attachment instead of a dozen files?

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.

More tools

The rest of the catalogue. Each tool still runs in your browser.

⭐

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.

⭐

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.

⭐

AES-GCM Secure Encrypted Notepad

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

⭐

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.

⭐

Area Converter

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

⭐

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.

⭐

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.

⭐

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.

⭐

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.

⭐

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.

⭐

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.

⭐

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.

⭐

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.

⭐

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.

⭐

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.

⭐

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.

⭐

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.

⭐

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.

⭐

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.

⭐

Chmod Calculator

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

⭐

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.

⭐

Code Minifier

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

⭐

Color Format Converter

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

⭐

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.

⭐

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.

⭐

Crontab Generator

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

⭐

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.

⭐

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.

⭐

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.

⭐

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.

⭐

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.

⭐

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.

⭐

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.

⭐

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.

⭐

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.

⭐

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.

⭐

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.

⭐

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.

⭐

Curl Converter

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

⭐

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.

⭐

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.

⭐

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.

⭐

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.

⭐

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.

⭐

Developer Secrets & Token Generator

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

⭐

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.

⭐

Discount Calculator

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

⭐

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.

⭐

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.

⭐

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.

⭐

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.

⭐

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.

⭐

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.

⭐

Fraction Calculator

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

⭐

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.

⭐

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.

⭐

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.

⭐

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.

⭐

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.

⭐

Grade Calculator

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

⭐

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.

⭐

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.

⭐

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.

⭐

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.

⭐

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.

⭐

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.

⭐

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.

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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.

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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.

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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.

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JSON / YAML / TOML / XML Serialization Converter

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

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JSON to TypeScript Converter

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

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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.

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Length Converter

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

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Loan Calculator

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

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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.

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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.

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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.

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Markdown Converter

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

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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.

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Math Worksheet Generator

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

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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.

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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.

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Mic Test

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

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Mortgage Calculator

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

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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.

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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.

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Number Base Converter

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

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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.

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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.

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Ovulation Calculator

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

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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.

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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.

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Password Hasher & Key Derivator

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

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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.

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Percentage Calculator

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

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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.

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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.

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Pregnancy Due Date Calculator

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

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Pressure Converter

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

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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.

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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.

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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).

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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.

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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.

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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.

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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.

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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.

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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.

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Random Team Generator

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

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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.

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Recipe Scaler

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

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Regex Tester Online

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

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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.

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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.

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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.

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Roman Numerals Converter

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

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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.

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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.

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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.

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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.

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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.

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Screen Resolution Checker

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

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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.

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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.

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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.

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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.

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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.

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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.

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Speaker Test

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

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Speed Converter

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

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SRI Hash Generator

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

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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.

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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.

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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.

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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.

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String Escaper — JSON, JS, SQL & Regex

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

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Subnet Calculator

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

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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.

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Temperature Converter

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

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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.

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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.

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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.

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Tip Calculator

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

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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.

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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.

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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.

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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.

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URL Parser & Query Inspector

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

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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.

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UTM Link Builder

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

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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.

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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.

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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.

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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.

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Volume Converter

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

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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.

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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.

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