Proportion Calculator

Solve proportions by finding the missing term in a/b = c/d.

Proportion Calculator helps you solve a/b = c/d for a missing value. Enter a (top of first fraction), b (bottom of first fraction), c (top of second fraction), and d (bottom of second fraction), review the breakdown, and use the guidance below to understand what the number means — and what it does not. What the Proportion calculator does Proportion Calculator is built for arithmetic, algebra, geometry, and number tools. Solve a/b = c/d for a missing value. You enter a (top of first fraction), b (bottom of first fraction), c (top of second fraction), and d (bottom of second fraction), then Simple Calculators computes the result instantly. Results use standard school and engineering formulas that run privately in your browser. How the math works Cross-multiply: a × d = b × c, then divide for the unknown. The formula: A/B = C/D, so A × D = B × C. Solve for any one value by dividing the other cross-product by its partner.