Three percentage calculations in one place: what is X% of Y, X is what percent of Y, and the percentage change from one value to another. Type into any box and the answer updates instantly; commas and dots both work as the decimal separator. Handy for discounts, sales tax, test scores, price rises and statistics.
How it works
Each line uses one standard formula. X% of Y = X ÷ 100 × Y. For example, 20% of 150 is 0.20 × 150 = 30. X is what percent of Y = X ÷ Y × 100. 30 out of 150 is 30 ÷ 150 × 100 = 20%. Percentage change from X to Y = (Y − X) ÷ |X| × 100. A positive result is an increase, a negative one a decrease. Going from 80 to 100 is (100 − 80) ÷ 80 × 100 = +25%. Results are rounded to two decimal places. Mind the difference between percent and percentage points: if an interest rate rises from 2% to 3%, it went up by one percentage point, but by 50 percent.
Worked example
A jacket costs $80 and goes on sale at 25% off. 25% of 80 is $20, so you pay $60. To check the discount the other way round, ask: 20 is what percent of 80? The answer is 25%. If the price later goes from $60 back up to $80, the change is +33.33%, not +25%, because a percentage change is always measured against the starting value.