▣ CALCULATORS Updated July 25, 2026

Proportion Calculator

Solve proportions and cross-multiply.

a
b
c
d (leave blank)
Result
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How it works

Leave exactly one box blank. Cross multiplication rearranges a/b = c/d to solve for the missing term.

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Frequently asked questions

What is cross multiplication?

Multiplying diagonally across the equals sign: a × d = b × c.

Can I use decimals?

Yes, any real numbers work as long as no denominator is zero.

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