What this calculator does
It answers the three questions people ask most often about percentages. You can fill in one row or all three at once.
- What is 15% of 80? Percent of a number.
- 12 is what percent of 48? Part as a percent of the whole.
- From 50 to 65, what is the % change? Increase or decrease.
How to use it
- Fill both boxes in at least one row.
- Press Calculate.
- Read the answer for each row and the steps below.
The formulas
Percent of a number = percent100 × number
What percent = partwhole × 100%
Percent change = new − oldold × 100%
Examples you can try
| Question | Answer |
|---|---|
| 15% of 80 | 12 |
| 12 is what % of 48 | 25% |
| 50 to 65 | +30% |
| 80 to 60 | −25% |
| 8.25% of 120 | 9.9 |
Where people use it
- Sale prices and sales tax: 8.25% of $120 is $9.90.
- Tips: 18% of $64.
- Grades: 42 out of 50 is 84%.
- Growth: how much did a price or a score change?
Tips
- Percent change is measured against the starting value, so going up 50% and then down 50% does not return you to where you began.
- To turn a ratio into percents, use the ratio to percentage calculator.
Want to learn the method?
How to turn a ratio into a percentageRead our short guide with worked examples you can follow on paper.
Frequently asked questions
How do I calculate a percentage of a number?
Divide the percent by 100 and multiply by the number. 15% of 80 is 0.15 × 80 = 12.
How do I find what percent one number is of another?
Divide the part by the whole and multiply by 100.
How is percent change calculated?
Subtract the old value from the new one, divide by the old value and multiply by 100.
Can percent change be negative?
Yes. A negative result means a decrease.
Why can the starting value not be zero?
Percent change divides by the starting value, and division by zero is undefined.