Calculator Tools

Ratio Calculator

Simplify two numbers or find the missing value in a proportion.

What would you like to do?

Reduce A:B to its simplest form

Use nonnegative decimal numbers in the same units. B and D are denominators and must be greater than zero.

Your numbers stay in this browser.

Result

Keep the relationship clear.

Enter both terms to find the smallest equivalent whole-number ratio.

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Two ways to work with ratios

A ratio compares quantities in the same units. A proportion says that two ratios are equal.

Simplify A:B

1920:1080 = 16:9. Dividing both terms by 120 keeps the same relationship.

Decimals work too: 0.1:0.3 = 1:3. The result is an exact whole-number ratio.

Find a missing value

3:4 = 9:D gives D = 12. Cross-multiply: 3 × D = 4 × 9, then divide by 3.

Choose which of A, B, C or D is unknown. The calculator uses the other three values and shows the check.

Before you calculate

Can a term be zero?

A and C can be zero, but denominators B and D must be greater than zero. For example, 0:5 simplifies to 0:1. The ratio 0:0 is undefined. A proportion such as 0:B=0:2 has no unique answer; 0:B=3:2 has no valid positive denominator. These cases are explained rather than returned as zero.

How are decimals and limits handled?

Each input accepts a nonnegative value up to 1 trillion, up to 6 effective decimal places and at most 64 characters. Trailing zeros do not count toward the decimal limit. Use a dot, without commas, units or exponent notation. The calculation keeps the exact fractional relationship. Rounded displays use at most 6 decimal places, or 6 significant digits for very small values, and show ≈. The exact fraction remains available.

Does this resize an image or convert units?

No. The tool calculates numeric ratios; it does not change a file, convert units, distribute a total or calculate percentage change. For percentage questions, use the Percentage Calculator.

Are my numbers stored or uploaded?

Your inputs, formulas and results stay in browser memory. Copying is optional. Only feedback you choose to send is submitted; calculation content is never attached. Development and QA visits send no analytics.