Proportion Calculator

Enter three known values in a proportion (A/B = C/D) and choose which one to solve for.

Proportion Calculator

Solve a proportion of the form A/B = C/D for the missing value, given the other three.

This calculator provides an estimate for general informational purposes only. It is not a substitute for professional financial, mechanical or engineering advice.

A proportion sets two ratios equal to each other. Cross-multiplying the known values and dividing isolates whichever term is missing.

Example

  • With the default values shown above, this calculator returns: D ≈ 15.00; C ≈ 0.00.

Frequently Asked Questions

What is a proportion?

A proportion states that two ratios are equal: A/B = C/D. Cross-multiplying gives A×D = B×C, which is rearranged to solve for whichever value is missing.

What is this used for?

Proportions are used in scaling recipes, map distances, currency conversion by rate, unit conversion, and any 'if A corresponds to B, what corresponds to C?' problem.

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