Percentage Calculator
Work out a percentage of a number, the reverse (“X is what percent of Y?”), or how much a value has gone up or down.
About this calculator
This calculator solves the percentage problems people run into most often: taking a percent of a value, asking what percent one number is of another, and measuring how much a value has changed. Those three modes cover tips, tax, discounts, score shares, and simple growth or decline comparisons. Results are arithmetic only—they are not financial, tax, or investment advice. Use the formula shown on this page so you can check the same steps on paper or in a spreadsheet.
How to calculate
Choose a calculation type, enter the two values, and press Calculate. Use “What is X% of Y?” for tips, tax, and discounts. Use “X is what % of Y?” to compare a part against a whole. Use percentage change to compare an old value with a new one. If a value is zero where division is required, the calculator will reject the input instead of returning an infinite or undefined result.
When to use it
- Tips and sales tax
- Exam scores as a share of the total
- Price or metric change between two periods
Examples
20% of 150
20 ÷ 100 × 150 = 30. So 20% of 150 is 30.
Price increase
If a price rises from 80 to 100, the change is ((100 − 80) / 80) × 100 = 25%.
Part of a whole
If 45 students passed out of 60, then 45 is (45 / 60) × 100 = 75% of the class.
Common percentages of 80, 100, and 250
| Percent | of 80 | of 100 | of 250 |
|---|---|---|---|
| 5% | 4 | 5 | 12.5 |
| 10% | 8 | 10 | 25 |
| 15% | 12 | 15 | 37.5 |
| 20% | 16 | 20 | 50 |
| 25% | 20 | 25 | 62.5 |
| 50% | 40 | 50 | 125 |