Five percentage questions, one tool
- X% of Y: divide X by 100 and multiply by Y. 20% of 150 = 0.2 × 150 = 30.
- X is what percent of Y: divide X by Y and multiply by 100. 30 out of 120 = 0.25 × 100 = 25%.
- Percentage change: take the difference, divide by the starting value and multiply by 100. From 80 to 100 = 20 ÷ 80 × 100 = +25%.
- Increase by a percentage: multiply by (1 + X/100). £250 plus 4% = £260.
- Decrease by a percentage: multiply by (1 − X/100). £80 less 15% = £68.
A common mistake
Percentage increases and decreases are not symmetrical. If a price rises by 25% from £80 to £100, taking 25% off £100 gives £75, not £80. To undo a 25% rise you need a 20% cut. The same applies to VAT: to remove 20% VAT you divide by 1.2, you don't subtract 20%. Our VAT calculator does that for you.
Percentage points vs percent
If an interest rate goes from 4% to 5%, it has risen by 1 percentage point but by 25 percent. News reports often mix the two up.
Everyday uses
Work out a pay rise, exam marks, a tip, a price change, a sale discount (try the discount calculator) or growth in followers or sales. The working is shown under each answer, so you can check it or copy the method into a spreadsheet. Everything runs in your browser.
Frequently asked questions
How do I work out a percentage of a number?
Divide the percentage by 100 and multiply by the number. 15% of 80 = 0.15 × 80 = 12.
How do I calculate percentage increase?
(New − Old) ÷ Old × 100. From 50 to 65 is a 30% increase.
How do I find what percent one number is of another?
Divide the part by the whole and multiply by 100. 18 out of 24 = 75%.
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