Calculators & Utilities

Proportion Calculator

Solve one missing value in the proportion a:b = c:d.

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Tool workspace

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Your result

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About the Proportion Calculator

The Proportion Calculator accepts exactly one blank field and solves the equality by cross multiplication. It shows the completed ratio and validates zero denominators.

How to use the Proportion Calculator

  1. Enter three known numbers and leave the unknown field blank.
  2. Solve the cross-multiplied equation.
  3. Substitute the result to verify both ratios.

Practical tips

  • Leave exactly one field empty.
  • A denominator of zero makes the ratio undefined.
Helpful answers

Proportion Calculator FAQs