Percentage Calculator
Three percentage questions, one tool: a percentage of a number, one number as a percentage of another, and the percentage change between two values. Covers homework, shopping, statistics and everyday money maths.
Percentage Calculator
Percents of, percents change, and more
How it works
- X% of Y = Y × X ÷ 100.
- X as a percentage of Y = X ÷ Y × 100.
- Percentage change = (new − old) ÷ old × 100.
- A rise from 50 to 100 is +100%; a fall from 100 to 50 is −50% — the base matters.
- Percentage points are not percent: an interest rate moving from 2% to 3% rises 1 point but 50%.
Worked example: price rise from €80 to €92
- 1Difference: 92 − 80 = 12.
- 2Divide by the old value: 12 ÷ 80 = 0.15.
- 3Multiply by 100: 0.15 × 100 = 15%.
The price increased by 15%
Handy percentage shortcuts
| To find | Trick | Example (of 240) |
|---|---|---|
| 50% | Halve it | 120 |
| 25% | Halve, then halve again | 60 |
| 10% | Move the decimal one place left | 24 |
| 5% | Half of 10% | 12 |
| 1% | Move the decimal two places left | 2.4 |
| 15% | 10% + 5% | 36 |
Frequently asked questions
How do I calculate a percentage increase?
Subtract the old value from the new one, divide by the old value and multiply by 100. From 80 to 100 is (100 − 80) ÷ 80 × 100 = 25%.
How do I find what percentage one number is of another?
Divide the part by the whole and multiply by 100. 45 out of 60 is 45 ÷ 60 × 100 = 75%.
What is the difference between percent and percentage points?
Percentage points measure the absolute gap between two percentages; percent measures the relative change. Unemployment rising from 4% to 5% is up 1 percentage point, which is a 25% increase.
How do I reverse a percentage change?
Divide by 1 plus the rate. If a price rose 20% to €120, the original was 120 ÷ 1.20 = €100 — not €96 (which is 20% off 120).
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