The four calculations you need most
Percentages show up in discounts, tips, taxes, grades, interest and price changes. Most questions fall into four types, and each has its own box above.
- What is X% of Y? Multiply Y by X and divide by 100. For example, 15% of 240 is 36.
- X is what percent of Y? Divide X by Y and multiply by 100. For example, 45 is 25% of 180.
- Percentage change from A to B: subtract A from B, divide by A and multiply by 100. For example, 80 to 100 is a 25% increase.
- Increase or decrease Y by X%: multiply Y by (1 + X/100) for an increase or (1 - X/100) for a decrease.
How to use the percentage calculator
- Pick the box that matches your question.
- Type the two numbers.
- Press Calculate, or press Enter, to see the answer with a short explanation.
Percentage change is not symmetrical
A rise of 25% followed by a fall of 25% does not bring you back to the start. Going from 80 to 100 is a 25% increase, but going from 100 back to 80 is a 20% decrease, because the percentage is measured against a different starting number.
This is why a stock that falls 50% needs a 100% gain to recover.
Percent vs percentage points
If an interest rate rises from 4% to 6%, it has risen by 2 percentage points, but by 50% in relative terms. News stories often mix these up, so check which one is meant.
Everyday uses
- Discounts: find the sale price and how much you save.
- Tips and tax: work out the amount to add to a bill.
- Grades: turn a score into a percentage.
- Business: track growth in sales, traffic or costs from one period to the next.
Common percentages as decimals and fractions
| Percentage | Decimal | Fraction |
|---|---|---|
| 5% | 0.05 | 1/20 |
| 10% | 0.1 | 1/10 |
| 12.5% | 0.125 | 1/8 |
| 20% | 0.2 | 1/5 |
| 25% | 0.25 | 1/4 |
| 50% | 0.5 | 1/2 |
| 75% | 0.75 | 3/4 |
Frequently Asked Questions
How do I calculate a percentage of a number?
Multiply the number by the percentage and divide by 100. 15% of 240 = 240 x 15 / 100 = 36.
How do I find what percent one number is of another?
Divide the first number by the second and multiply by 100.
How do I calculate percentage change?
Subtract the old value from the new value, divide by the old value and multiply by 100.
How do I take a discount off a price?
Use the decrease box. Decreasing 80 by 15% gives 68.
Why can't the starting value be zero?
A percentage change from zero is undefined, because you cannot divide by zero.
Is my data stored?
No. The calculation runs in your browser, so the numbers you enter are not sent to our server.