Proportion Calculator

Set the two ratios equal and use cross multiplication. For a:b = c:x, multiply b by c and divide by a to find x.

Solve proportions and find missing values using equivalent ratios and cross multiplication.

A : B = C : D

Leave exactly one value blank to solve for it.

Proportion Formula

For: A : B = C : D Cross multiplication: A × D = B × C Examples: D = (B × C) ÷ A C = (A × D) ÷ B B = (A × D) ÷ C A = (B × C) ÷ D

A proportion compares two equivalent ratios. Cross multiplication converts the proportion into an equation that can be solved for the missing value.

Enter any three values in the proportion. Leave exactly one value blank.

Multiply the terms diagonally across the proportion.

Divide by the remaining known coefficient to find the missing value.

Scale ingredient quantities while maintaining the same proportions.

Convert distances and measurements using scale relationships.

Find missing quantities when prices, rates or amounts are proportional.

Maintain consistent proportions when combining quantities or solutions.

A proportion is an equation stating that two ratios or fractions are equal, such as 2:3 = 8:12.

Set the two ratios equal and use cross multiplication. For A:B = C:x, multiply B by C and divide by A to find x.

Cross multiplication multiplies the numerator of one fraction by the denominator of the other. For A/B = C/D, the equation becomes A × D = B × C.

Yes. Proportions can contain decimals as long as the denominators used in the calculation are not zero.