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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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Result

A ratio compares two quantities — 2 cups of flour to 1 cup of water, 16 units of width to 9 of height, 3 parts blue paint to 4 parts white. This ratio calculator does all the routine work around ratios in one place: it simplifies any ratio to lowest terms, solves proportions of the form A : B = C : x, scales both sides by any factor to build equivalent ratios, and converts a ratio into a fraction, a decimal and a percentage.

The math is exact. Both sides are first turned into whole numbers (2.5 : 1 becomes 25 : 10), the greatest common divisor is found with the Euclidean algorithm, and all multiplication and division is done in arbitrary-precision integer arithmetic — so 25 : 10 reliably simplifies to 5 : 2 and a proportion like 3 : 4 = 9 : x yields exactly x = 12, never 11.999…. Every transformation is listed as a numbered step, the way a teacher would write it on the board.

Typical jobs: scale a recipe from 4 servings to 6, convert a map scale, keep a paint or cocktail mix consistent at a different volume, compare unit prices, or express a screen ratio as a percentage. If your ratio is specifically the width and height of a screen or image, the dedicated aspect ratio calculator on this site computes missing pixel dimensions for you; and when you need full arithmetic on fractions — adding or dividing them — the fraction calculator picks up where ratios end.

Everything runs locally in your browser: nothing is uploaded, there is no registration, and the calculator is free for any number of calculations on desktop and mobile alike.

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Executed in Browser

Your files and inputs never leave this device. Processing runs completely offline. 100% Secure.

Accepted Formats & Rules

  • 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.

Key Benefits

✓ Every answer comes with the full step-by-step working, so you can follow the method and check homework.
✓ Exact integer arithmetic under the hood — decimal inputs like 2.5 : 1 are scaled to whole numbers, never rounded.
✓ Runs entirely in your browser: no sign-up, no uploads, instant results on any device.

Use Cases

  • • Simplify a ratio like 25:10 or 2.5:1 to its lowest terms with the GCD steps shown, ready to paste into homework.
  • • Solve a proportion such as 3:4 = 9:x by cross-multiplication to scale a recipe, a map distance or a price exactly.
  • • Convert a ratio to a fraction, decimal and percentage at once to compare test scores, mixes or screen shapes.