Ratio Calculator

Simplify a ratio, solve the blank in a proportion, or scale both sides by the same factor.

Calculation
Results
Simplified ratio
Share of total
As a decimal
Enter both parts of a ratio — the simplest form appears instantly.

Every calculation happens in your browser — the numbers you type never leave your device.

FAQ

How is a ratio simplified?

Both parts are converted to whole-number terms and divided by their greatest common divisor. For example, 12:18 becomes 2:3, and 0.5:1.25 becomes 2:5.

How do I find a missing value?

Open Missing value, fill three boxes in A:B = C:D, and leave the unknown box empty. The calculator keeps the two ratios equivalent and shows the completed proportion.

What does scaling a ratio do?

Scaling multiplies both parts by the same factor, so the relationship stays the same. A 2:3 ratio scaled by 4 becomes 8:12, while its simplest form is still 2:3.

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