Math

How to Use a Ratio Calculator

Learn how ratios work and how to simplify a ratio between two numbers.

Updated June 24, 2026

A ratio compares two values. A ratio calculator helps reduce two numbers into their simplest comparison.

Related toolRatio Calculator

Use the calculator first, then read the guide below to understand the formula and examples.

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Direct answer

To use a ratio calculator, enter the two values you want to compare. The calculator finds the greatest common factor and divides both numbers by it.

Formula idea

Simplified ratio = first value ÷ common factor : second value ÷ common factor.

Example

If the values are 20 and 30, the greatest common factor is 10. Divide both values by 10 and the simplified ratio becomes 2:3.

Where ratios are used

Ratios are used in recipes, maps, design, finance, classrooms, mixtures, comparisons, and scaling measurements.

Common mistake

Do not treat a ratio as a percentage unless the question asks for a percentage. A ratio compares parts directly, while a percentage compares a value to 100.

FAQs

What does 2:3 mean?

It means the first value has 2 parts while the second value has 3 parts.

Can a ratio use decimals?

Ratios can start with decimals, but simplified ratios are usually shown as whole numbers when possible.

Is 20:30 the same as 2:3?

Yes. 20:30 simplifies to 2:3.

Try the calculator

Use the Ratio Calculator to check your own numbers quickly.

Use Ratio Calculator