How it works
A proportion states that two ratios are equal. Cross-multiplying both sides and rearranging gives x = (B × C) ÷ A.
Formula: A : B = C : x, so x = (B × C) ÷ A
Examples
Scaling a recipe
If 2 cups of flour need 3 eggs, how many eggs for 6 cups? 2 : 3 = 6 : x gives x = (3 × 6) ÷ 2 = 9.
Things to keep in mind
- A cannot be zero, since it is the calculation's denominator.
- Enter values of zero or more: like the Ratio Calculator, this treats A, B and C as quantities being compared, which is not meaningful for a negative value.