How to use this tool
- Pick the box that matches your question.
- Type the two numbers. Decimals and negative numbers are fine.
- Read the answer and the formula underneath. Copy the result into your work.
The three percentage formulas
Percent of a number: divide the percent by 100 and multiply by the number. 15% of 240 is 0.15 × 240 = 36. This is the sum behind discounts, tips and commission.
What percent one number is of another: divide the part by the whole and multiply by 100. 45 out of 60 is 75%. Teachers use this for exam marks and shops use it for stock levels.
Percentage change: subtract the old value from the new one, divide by the old value and multiply by 100. Going from 80 to 100 is a 25% increase, but going from 100 back to 80 is a 20% decrease. The base changes, so the percentages differ.
Percentage points vs percent
If an interest rate moves from 4% to 5%, it has gone up by one percentage point, which is a 25% increase in the rate itself. News reports often mix the two up, so it helps to be clear which one you mean.
Shopping a sale? The discount calculator works out the final price after one or two discounts.
Frequently asked questions
How do I work out a percentage of a number?
Divide the percentage by 100, then multiply by the number. For example, 20% of 50 is 0.2 × 50 = 10.
How do I calculate percentage increase?
Subtract the original value from the new value, divide by the original value, then multiply by 100.
How do I find what percent one number is of another?
Divide the smaller part by the total and multiply by 100. 30 out of 120 is 25%.
Why is a 50% drop not undone by a 50% rise?
Because the second percentage is taken from a smaller base. 100 falls to 50, but 50% of 50 is only 25, so you end at 75.