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Ratio Calculator

Enter a ratio to simplify it, see it as a decimal, and scale it so the first term equals any number.

  • 2 : 3Simplified ratio
  • 0.6667As a decimal (a ÷ b)
100 : 150

scaled equivalent ratio

How to use it

  1. Enter the two terms Type the ratio as a : b.
  2. Read the simplified form It's reduced using the greatest common divisor.
  3. Scale it Set a target first term to rescale the ratio.

Examples

8 : 12 2 : 3
scale 2:3 to 10 10 : 15

About this tool

A ratio compares two quantities, and the clearest way to read one is in its simplest whole-number form. This tool reduces any ratio using the greatest common divisor and also shows the equivalent decimal, so you can compare values at a glance.

Need to keep proportions while changing the numbers — doubling a recipe, mixing paint, or scaling a drawing? Enter a target for the first term and the tool rescales the second to match. It all runs in your browser.

Frequently asked questions

How is the ratio simplified?

Both terms are divided by their greatest common divisor, giving the smallest whole-number ratio with the same value.

What does scaling do?

It finds an equivalent ratio with the first term you specify — useful for recipes, mixes and scale drawings.

Related tools

Fraction Calculator Enter two fractions and an operation to get a simplified result, with decimal and mixed-number forms. Percentage Calculator Three percentage calculators in one — find a percentage of a number, a ratio as a percentage, and percentage change. Prime Number Checker Test any whole number for primality and, if it is composite, see its prime factors. Average Calculator Calculate the mean, median, mode, range, sum and count of any list of numbers. GCD & LCM Calculator Enter a list of whole numbers to get their GCD and LCM at once. Quadratic Equation Solver Enter the coefficients a, b and c to find the roots, discriminant and vertex of a quadratic equation.

Updated June 13, 2026