Help & FAQ
How to use the Percentage Calculator
How to use the percentage calculator
- Pick the type of question you are answering from the tabs above.
- Type your two numbers. The answer updates as you type.
- Check the formula line under the result to see exactly how it was worked out, then copy the answer if you need it.
Percentage formulas
| Question | Formula | Example |
|---|---|---|
| What is P% of X? | X × P ÷ 100 | 20% of 150 = 30 |
| A is what % of B? | A ÷ B × 100 | 30 is 20% of 150 |
| % change from A to B | (B − A) ÷ |A| × 100 | 80 → 100 is +25% |
| X increased by P% | X × (1 + P ÷ 100) | 250 + 15% = 287.5 |
| X is P% of what? | X ÷ (P ÷ 100) | 30 is 20% of 150 |
Results are shown to up to six decimal places and rounded half away from zero. Division by zero is not allowed: a percentage of a total of 0, or a change from a starting value of 0, has no meaningful answer.
Everyday examples
- Tips: a 12% tip on a 45.00 bill is 5.40.
- Exam scores: 42 correct out of 60 is 70%.
- Salary rises: going from 3,200 to 3,400 a month is a 6.25% raise.
- Prices with tax: 59.99 plus 24% VAT is 74.39.
How do I calculate a percentage of a number?
Multiply the number by the percentage, then divide by 100. For example, 15% of 80 is 80 × 15 ÷ 100 = 12.
Why isn't a 20% increase followed by a 20% decrease back to the start?
Because the decrease is taken from the larger number. 100 + 20% = 120, and 120 − 20% = 96. To undo a 20% increase you need a decrease of about 16.67%.
What is the difference between percentage change and percentage points?
If an interest rate goes from 2% to 3%, it rose by 1 percentage point, but by 50% in relative terms. This calculator's "% change" mode gives the relative change.
How do I remove VAT or sales tax from a price?
Use Reverse %. A price of 120 that includes 20% tax is 120% of the net price, so enter 120 and 120% to get 100.