Percentage Calculator
Calculate percentages, increases, and decreases quickly and accurately.
How the calculator works
All three modes are rearrangements of one relationship: a percentage is a fraction of 100. To find a percentage of an amount, the calculator multiplies the amount by the percentage and divides by 100 — so 25% of 200 is 200 × 25 ÷ 100 = 50. To find what percentage one number is of another, it divides the first by the second and multiplies by 100, which is how a test score of 43 out of 50 becomes 86%. To measure percentage change, it subtracts the old value from the new one, divides by the absolute value of the old figure, and multiplies by 100. Increases come out positive and decreases negative — and because the comparison is always against the old value, a rise from 80 to 100 is +25%, while a fall from 100 to 80 is −20%.
Formula
What percent X is of Y: Percentage = X ÷ Y × 100
Percentage change: Change % = (New − Old) ÷ |Old| × 100
Where:
- X — the percentage or the first value
- Y — the amount or the second value
- Old / New — the two values being compared
- |Old| — the absolute (unsigned) old value
Example
A jacket is priced at $120 with a “30% off” tag. Mode one gives 120 × 30 ÷ 100 = 36, so the discount is $36 and you pay $84. If your salary rises from 2,400 to 2,700, mode three gives (2,700 − 2,400) ÷ 2,400 × 100 = +12.5%. And if you answered 43 of 50 exam questions correctly, mode two gives 43 ÷ 50 × 100 = 86%.