Proportion Calculator

Solve proportions using cross multiplication. Find any missing value in a/b=c/d with step-by-step solutions.

Solve For Missing Value

Enter 3 known values to find the 4th

Direct Proportion: a/b = c/d Inverse Proportion: a×b = c×d

Ratio (Simplified)

Decimal

Solution Steps

Formulas

Direct Proportion

a/b = c/d → a×d = b×c

Inverse Proportion

a×b = c×d

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Pro Tips

Cross multiplication works by multiplying opposite corners: a×d = b×c.

Direct proportion: as one variable increases, the other increases proportionally.

Inverse proportion: as one variable increases, the other decreases (a×b = constant).