Proportion Calculator

➗ Proportion Solver

A : B = C : D

Cross-multiply to find the missing value

A

B

C

D (to find)

Formula

D = (B × C) / A

Since A/B = C/D, we multiply both sides by B×D:
A×D = B×C
Therefore: D = (B × C) / A

1

Set up the proportion - If A is to B as C is to D, write A:B = C:D

2

Cross-multiply - Multiply A by D and B by C

3

Solve for the unknown - Divide the product by the remaining known value

Cooking Recipe

If 2 cups of flour make 24 cookies, how much flour for 60 cookies?
2:24 = X:60 → X = (24 × 60) / 2 = 5 cups

Map Scale

If 1 inch on a map equals 50 miles, how many miles is 3.5 inches?
1:50 = 3.5:X → X = (50 × 3.5) / 1 = 175 miles