Formulas
- X% of Y = X ÷ 100 × Y
- A is what percent of B = A ÷ B × 100
- Percent change = (new − old) ÷ |old| × 100
Examples
15% of 200 is 30. 50 is 25% of 200. Going from 80 to 100 is a 25% increase, but going from 100 back to 80 is a 20% decrease, because the base changes. This asymmetry is why percentage points and percent change are different things.
Percentage points versus percent
If an interest rate rises from 4% to 5%, it rises by 1 percentage point, which is a 25% relative increase. When a figure is already a percentage, say which one you mean.