Proportion Calculator

Solve proportions: find the missing value in a/b = c/d.

Solve For Missing Value

Enter 3 known values to find the 4th

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

Enter your values above to see the result.

Ratio (Simplified)

Decimal

Step-by-step Solution

Formulas

Direct Proportion

a/b = c/d → a×d = b×c

Inverse Proportion

a×b = c×d

Related Calculators

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).