Percentage Calculator
Three common percentage questions answered from the same two numbers.
The three formulas
With the default numbers, 20 and 150:
- X% of Y = Y × X ÷ 100. 20% of 150 is 30.
- X is what percent of Y = X ÷ Y × 100. 20 is 13.33% of 150.
- Percent change from X to Y = (Y − X) ÷ X × 100. Going from 20 to 150 is a change of +650%.
Percent change depends on the starting value. Going back down from 150 to 20 is a change of -86.67%, not −650%. A price that rises 50% and then falls 50% ends up 25% below where it started.
Fractions, decimals, and percentages
| Fraction | Decimal | Percent |
|---|---|---|
| 1/2 | 0.5 | 50% |
| 1/3 | 0.3333 | 33.33% |
| 2/3 | 0.6667 | 66.67% |
| 1/4 | 0.25 | 25% |
| 3/4 | 0.75 | 75% |
| 1/5 | 0.2 | 20% |
| 1/8 | 0.125 | 12.5% |
| 1/10 | 0.1 | 10% |
| 1/20 | 0.05 | 5% |
| 1/100 | 0.01 | 1% |
Percentage points versus percent
When a rate moves from 5% to 7%, it has risen by 2 percentage points, which is a 40% increase relative to where it started. News reports and bank statements use both, so it is worth checking which one is meant.
Where each question comes up
"X% of Y" covers tips, tax, commission, and discounts. "What percent" covers test scores and budgets: 24 out of 30 is 80%. "Percent change" covers prices, salaries, and investment returns. Related calculators handle the common cases directly: discounts, sales tax, and tips.