Percentage Calculator
Five quick percentage calculators in one place. Type your numbers and the answer appears instantly.
By Shah Rukh, software developer · Last updated:
Percentage formulas
| Question | Formula | Example |
|---|---|---|
| What is X% of Y? | Y × X ÷ 100 | 15% of 200 = 30 |
| A is what % of B? | A ÷ B × 100 | 30 of 120 = 25% |
| Percentage change | (New − Old) ÷ |Old| × 100 | 80 → 100 = +25% |
| Increase by X% | N × (1 + X ÷ 100) | 50 + 20% = 60 |
| Decrease by X% | N × (1 − X ÷ 100) | 50 − 20% = 40 |
| Percentage difference | |A − B| ÷ ((A + B) ÷ 2) × 100 | 40 vs 60 = 40% |
Percentage change vs percentage difference
Use percentage change when there’s a before and after, like a price going from 80 to 100 (+25%). Use percentage difference to compare two values with no order, like two shops’ prices. It divides by the average, so the result is the same whichever value comes first.
Quick mental tricks
- 10% of any number: move the decimal point one place left (10% of 250 = 25).
- 5% is half of 10%; 20% is double 10%.
- X% of Y equals Y% of X: 8% of 50 is the same as 50% of 8, which is 4.
Shopping? The discount calculator handles sale prices and stacked discounts. Grades? Try percentage to letter grade.
Frequently asked questions
How do I calculate a percentage of a number?
Multiply the number by the percentage and divide by 100. For example, 15% of 200 = 200 × 15 ÷ 100 = 30.
How do I work out a percentage increase?
Subtract the old value from the new one, divide by the old value and multiply by 100. From 80 to 100: 20 ÷ 80 × 100 = 25%.
Why isn’t a 50% drop undone by a 50% rise?
Because each percentage applies to a different starting value. 100 − 50% = 50, but 50 + 50% = 75.
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