Percentage Calculator
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Results
15% of 80 is 12
How to use the percentage calculator
- Choose the question you want answered from the list.
- Enter the numbers. Negative values are allowed, for example for a fall in price.
- The answer and the formula update as you type. Copy the link to share the exact calculation.
Percentage formulas
X as a percent of Y = X ÷ Y × 100
Percentage change = (B − A) ÷ |A| × 100
Percentage difference = |A − B| ÷ ((|A| + |B|) ÷ 2) × 100
"Percent" means "per hundred", so a percentage is just a fraction with 100 as the denominator. For example, going from 80 to 100 is a change of 25%, while going back from 100 to 80 is a change of -20%: the starting value is different, so the percentages are too.
Common percentages
| Percent | As a decimal | Of 200 |
|---|---|---|
| 5% | 0.05 | 10 |
| 10% | 0.1 | 20 |
| 12.5% | 0.125 | 25 |
| 15% | 0.15 | 30 |
| 20% | 0.2 | 40 |
| 25% | 0.25 | 50 |
| 33.33% | 0.3333 | 66.66 |
| 50% | 0.5 | 100 |
| 75% | 0.75 | 150 |
Tips for working with percentages
- Percentage points are not percentages. A rate rising from 4% to 5% is up 1 percentage point, which is a 25% increase in the rate.
- Successive changes multiply. Two 10% increases make 1.1 × 1.1 = 1.21, a 21% increase, not 20%.
- Swap the numbers to check. P% of Y always equals Y% of P: 8% of 50 is the same as 50% of 8.
Frequently asked questions
How do I calculate a percentage of a number?
Divide the percentage by 100 and multiply by the number. For example, 15% of 80 is 15 ÷ 100 × 80 = 12.
How do I work out what percent one number is of another?
Divide the part by the whole and multiply by 100. For example, 12 is 12 ÷ 80 × 100 = 15% of 80.
How do I calculate percentage increase or decrease?
Subtract the old value from the new value, divide by the old value and multiply by 100. Going from 80 to 100 is (100 − 80) ÷ 80 × 100 = a 25% increase; going from 100 to 80 is a 20% decrease.
What is the difference between percentage change and percentage difference?
Percentage change measures a move from a starting value, so the direction matters. Percentage difference compares two values with neither as the starting point, dividing the gap by their average: 80 and 100 differ by about 22.2%.
Why does a 20% decrease not undo a 20% increase?
Because each percentage is taken of a different starting value. Increasing 100 by 20% gives 120, but 20% of 120 is 24, so decreasing 120 by 20% gives 96, not 100.