Quick answer
Type your numbers into any of the four calculators and the answer appears instantly. For example, 15% of 200 is 30, 30 is 25% of 120, and going from 80 to 100 is a 25% increase.
- Calculators:
- 4 in one page
- Results:
- Instant, as you type
- Formulas:
- Shown on this page
- Price:
- Free
- Sign-up:
- Not required
- Works on:
- Any device
Discounts, tips, tax, exam scores, sales growth — percentages are everywhere. This percentage calculator gives you the answer immediately and explains the maths, so you can check it yourself.
How to use Percentage Calculator – step by step
- 1 Pick the right calculatorChoose the box that matches your question.
- 2 Enter your numbersResults update as you type.
- 3 Read the answerIncreases show in green, decreases in red.
Why use our Percentage Calculator?
All common questions
Percent of, percent of total, change, increase and decrease.
Instant
No “calculate” button needed.
Accurate
Results to up to four decimal places.
Mobile friendly
Big inputs that are easy to use on a phone.
Percentage formulas
| Question | Formula | Example |
|---|---|---|
| What is X% of Y? | X ÷ 100 × Y | 15% of 200 = 30 |
| X is what % of Y? | X ÷ Y × 100 | 30 of 120 = 25% |
| % change from A to B | (B − A) ÷ A × 100 | 80 → 100 = +25% |
| Increase A by X% | A × (1 + X ÷ 100) | 100 + 20% = 120 |
| Decrease A by X% | A × (1 − X ÷ 100) | 100 − 20% = 80 |
A common percentage mistake
A 50% increase followed by a 50% decrease does not bring you back to where you started. 100 → 150 (+50%) → 75 (−50%). That’s because the second percentage is calculated on the new, larger number.
Frequently asked questions
How do I calculate a percentage of a number?
How do I calculate percentage increase?
How do I work out a discount?
What if the starting value is zero?
Last updated November 2026 · Written and tested by the SmallEasyTools team.