About this tool
Four everyday percentage calculations in one place: what is X% of a number, what percent one number is of another, the percentage increase or decrease between two values, and a number increased or decreased by a percentage. Useful for discounts, VAT, marks, salary rises and price changes.
How to use it
- Find the line that matches your question.
- Type the two numbers into it.
- The answer updates as you type.
Good to know
- Use a minus sign in the last calculator to decrease, e.g. −20 for a 20% discount.
- Percentage change is measured from the first number, so 80 → 100 is +25% but 100 → 80 is −20%.
- Results are rounded to four decimal places.
Frequently asked questions
How do I calculate a discount?
Use “increased by” with a negative percentage: 250 increased by −20 gives 200, the price after a 20% discount.
Why is a 25% rise not undone by a 25% fall?
Each percentage is taken from a different starting value. 80 + 25% is 100, but 100 − 25% is 75.