Ratio Calculator

Simplify a ratio A : B to its smallest whole numbers and solve for the missing value X in the proportion A : B = C : X.

About Ratio Calculator

A ratio compares two quantities, and a proportion states that two ratios are equal. To simplify A : B, this calculator multiplies both sides by a power of ten to clear any decimals, then divides them by their greatest common divisor. To solve A : B = C : X it cross-multiplies: X = B × C ÷ A. The proportion row appears only when C is filled in and A is not zero.

How to use Ratio Calculator

Fill in "A", "B" and "C".
The result appears below and updates as you type.
Copy the result with the copy button, or download it as a file where that is offered.

Questions about Ratio Calculator

How do I scale a recipe or mix with this?

Enter the original ratio as A and B, then the new amount of the first ingredient as C. X is the matching amount of the second. With 4 : 6 and C = 10, X is 15.

Runs in your browser. Page last updated November 12, 2026.

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