Percentage calculator

How it works

A percentage is a fraction of 100. To find X% of Y, divide X by 100 and multiply by Y.

To find what percent A is of B, divide A by B and multiply by 100. To find the whole when you know a part and its percentage, divide the part by the percentage and multiply by 100.

For a change from an old value to a new one, divide the difference by the old value. Adding 15% is the same as multiplying by 1.15; subtracting 15% is multiplying by 0.85.

Formula

X% of Y = X ÷ 100 × Y
A as % of B = A ÷ B × 100
Whole = part ÷ P × 100
% change = (new − old) ÷ |old| × 100
Y ± X% = Y × (1 ± X ÷ 100)

Worked example

15% of 240 is 15 ÷ 100 × 240 = 36. 36 is 15% of 240, because 36 ÷ 15 × 100 = 240. Going from 80 to 100 is a change of (100 − 80) ÷ 80 × 100 = 25%. Adding 15% to 240 gives 240 × 1.15 = 276.