Ratio calculator

Simplify a ratio to its lowest terms, or find a missing value in an equivalent ratio.

Simplify a ratio

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Simplified ratio

Find a missing value (A : B = C : ?)

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Missing value (D)

Full ratio—

How ratio simplification works

Simplifying a ratio means dividing both sides by their greatest common divisor (GCD), the same way you'd reduce a fraction. A ratio of 24:36 and a ratio of 2:3 describe the exact same relationship between two quantities — the simplified form is just easier to read and compare at a glance.

Solving equivalent ratios

Two ratios are equivalent when one is a scaled-up or scaled-down version of the other. Given A:B = C:D, you can find the missing value with cross-multiplication: D = (B × C) ÷ A. This is the same method used for recipe scaling, map distances, mixing concentrations, or converting between units that share a fixed proportion.

Where ratios show up in real life

Scaling a recipe up or down while keeping ingredient proportions correct
Mixing paint, fuel, or cleaning solutions to a specific concentration
Reading maps and scale models (e.g. 1:50,000)
Financial ratios like debt-to-income or price-to-earnings

This calculator only handles simple two- and three-term numeric ratios — for unit conversions or currency, use a dedicated conversion calculator instead.