⚖️ Proportion Calculator

Solve direct and inverse proportions instantly by entering three known values.

Type of proportion

If A =

then B =

If A =

then B =

Enter the three known values

Real-world examples

Direct proportion: If 3 litres of paint cover 30 m², how much paint do I need for 75 m²? → A=3, B=30, C=75, X=7.5 litres.

Direct proportion: A recipe for 4 people needs 200g of flour. How much for 6 people? → A=4, B=200, C=6, X=300g.

Inverse proportion: 6 workers finish a job in 8 days. How long for 4 workers? → A=6, B=8, C=4, X=12 days.

Frequently asked questions

What is the difference between direct and inverse proportion?

In direct proportion both quantities change in the same direction — if one doubles, the other doubles too. In inverse proportion they change in opposite directions — if one doubles, the other halves.

How do I know if a proportion is direct or inverse?

Ask: if A increases, does B increase or decrease? If increase → direct. If decrease → inverse. Example: more speed, less time → inverse.

What is cross-multiplication?

For direct proportion: X = (B × C) ÷ A. For inverse proportion: X = (A × B) ÷ C. This calculator applies the correct formula automatically.