How do I find a missing value in a ratio?

Enter the A:B ratio and either the A or B value. The calculator applies cross-multiplication to find the unknown value.

How does ratio simplification work?

The tool divides both A and B by their greatest common divisor (GCD) to express the ratio in its simplest form.

What are equivalent ratios?

Equivalent ratios represent the same proportion at different scales. For example 1:2, 2:4, 3:6 are all equivalent. The tool shows the first several multiples.

Ratio Calculator

Solve ratios, simplify A:B, and find missing values.

Ratio A : B

Known value

Simplified ratio

3 : 4

Equivalent ratios

3 : 46 : 89 : 1212 : 1615 : 2018 : 2421 : 2824 : 32

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FAQ

How do I find a missing value in a ratio?: Enter the A:B ratio and either the A or B value. The calculator applies cross-multiplication to find the unknown value.
How does ratio simplification work?: The tool divides both A and B by their greatest common divisor (GCD) to express the ratio in its simplest form.
What are equivalent ratios?: Equivalent ratios represent the same proportion at different scales. For example 1:2, 2:4, 3:6 are all equivalent. The tool shows the first several multiples.

Ratio Calculator lets you enter an A:B ratio and one known value to find the other (e.g. given 3:4 and A=9, find B=12). It also simplifies any ratio to its lowest terms using GCD, and shows a table of equivalent ratios.