About the Percentage Calculator
Four percentage calculators in one: find a percentage of a number, work out what percent one number is of another, measure the percentage change between two values, and increase or decrease a value by a percentage.
Key features
- X% of Y, e.g. 15% of 200
- X is what percent of Y
- Percentage change (increase or decrease) between two values
- Increase or decrease a value by a percentage
- Formula shown for every result
- Results update as you type
Four percentage calculators in one
Percentages come up everywhere: discounts, tips, tax, exam scores, statistics, salary rises and investment returns. This page answers the four most common percentage questions side by side.
Formulas
| Question | Formula | Example |
|---|---|---|
| What is X% of Y? | Y × X ÷ 100 | 15% of 200 = 30 |
| X is what % of Y? | X ÷ Y × 100 | 30 of 120 = 25% |
| % change from X to Y | (Y − X) ÷ X × 100 | 80 → 100 = +25% |
| Y increased by X% | Y × (1 + X ÷ 100) | 250 + 20% = 300 |
| Y decreased by X% | Y × (1 − X ÷ 100) | 250 − 20% = 200 |
Everyday examples
- Exam score: 42 out of 50 → 42 ÷ 50 × 100 = 84%.
- Salary rise: 52,000 to 55,000 → (55,000 − 52,000) ÷ 52,000 × 100 = 5.77%.
- Price drop: a laptop from 1,200 to 900 → −25%.
- Reverse percentage: if 120 includes a 20% increase, the original was 120 ÷ 1.2 = 100 (not 120 − 20%).
Common mistakes
- Dividing by the wrong base. Percentage change always divides by the original value.
- Adding percentages that apply in sequence. Two 10% discounts are 19% off, not 20%.
- Confusing percent and percentage points, especially with interest rates and statistics.
Related calculators
For shopping, use the Discount Calculator; for VAT and GST, the Sales Tax Calculator; for margins, the Profit Margin Calculator.
How to use the Percentage Calculator
- Enter your numbers in the fields above. Units and options can be changed at any time.
- The result updates instantly as you type; there's no calculate button to press.
- Check the breakdown under the main result for the details behind the number.
- Adjust the inputs to compare scenarios, for example a different rate or term.