What is X% of Y?
Result = (X ÷ 100) × Y. Example: 15% of 200 = 0.15 × 200 = 30. Use this for discounts, tips, tax estimates, and commission.
What percent is X of Y?
Percent = (X ÷ Y) × 100. Example: 40 of 200 = (40 ÷ 200) × 100 = 20%. Useful for grades, win rates, and completion progress. Y cannot be zero.
Percent change
Change % = ((new − old) ÷ |old|) × 100. Going from 100 to 125 is a 25% increase; from 125 to 100 is a 20% decrease. Absolute value in the denominator keeps the direction in the sign of the result.
Practice free
The CalcNest percentage calculator covers all three cases with copyable results. Related: how to calculate a discount and how to calculate a tip.