Ratio Calculator
Simplify a ratio to its lowest terms or solve a proportion where one of the four values is missing.
Enter two numbers to reduce the ratio A:B to its lowest terms.
Simplified ratio
2 : 3
As a quotient
0.6667
A ÷ B
As a percent
66.6667%
A is this percent of B
How to use the ratio calculator
Ratios show up in recipes, scale drawings, map legends, paint mixing, finance, and statistics. Two tasks cover most of what people need: simplifying a ratio (4:12 → 1:3) and solving for a missing piece of a proportion (3:5 = 12:?).
Simplify mode
- Enter the two numbers you want to simplify.
- The tool divides both by their greatest common divisor and shows the reduced form along with the decimal quotient and percent.
- If either value is a decimal, both are scaled to whole numbers before reducing.
Proportion mode
- A proportion is the statement A:B = C:D. Two ratios are equal when A×D = B×C.
- Leave exactly one of the four fields blank — the tool solves for it using cross-multiplication.
- Common use: scaling a recipe. If 2 eggs go with 3 cups of flour (2:3) and you have 9 cups of flour, leave the last field blank to find you need 6 eggs.
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