Percentage calculator

The four percentage sums

Each line of the calculator shows its working underneath, so you can check it or do it yourself next time.

A percentage of a number

Divide the percentage by 100 and multiply by the number. 15% of 80 is 15 ÷ 100 × 80 = 12. Handy for tips and discounts: a 20% tip on a 64 bill is 12.80.

What percent one number is of another

Divide the part by the whole and multiply by 100. 30 out of 120 is 30 ÷ 120 × 100 = 25%. Use it for test scores, budgets or how much of a target you’ve reached.

Percentage change

Take the new number minus the old one, divide by the old one, and multiply by 100. A price going from 80 to 100 is (100 − 80) ÷ 80 × 100 = +25%. Going back from 100 to 80 is −20%, not −25%, because the starting point is different. This is why a 50% fall needs a 100% rise to get back to where you started.

Adding or taking off a percentage

Multiply by 1 plus the percentage as a decimal. 250 with 20% off is 250 × 0.8 = 200; 250 plus 20% is 250 × 1.2 = 300. Type a minus sign for a decrease.

To reverse a percentage, divide instead of subtracting. If 300 already includes a 20% markup, the original is 300 ÷ 1.2 = 250, not 300 minus 20%. Our VAT calculator does this for sales tax.

Percent or percentage points?

When a 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 about interest rates and tax rates usually mean percentage points.