How to work out a percentage of a number, and the other way round.
How to work out 20% of 85, what percent 17 is of 85, and the other everyday percentage sums, with the formula and the steps on your own numbers.
By Suraj Kumar4 min read
Per cent means out of a hundred. Almost every percentage question is one of a handful of sums, and each takes two steps once you know which it is.
A percentage of a number.
Divide the percentage by 100 and multiply. 20% of 85 is 0.2 × 85 = 17. The Percentage calculator shows those two steps with your numbers, and a grid of 100 squares with 20 filled.
What percent one number is of another.
Divide the part by the whole and multiply by 100. 17 is 17 ÷ 85 × 100 = 20% of 85. When the division does not come out even, the answer is rounded to the places you choose, and the page says it is rounded.
Changes, discounts and working back.
A rise or fall is measured against where it started; a discount is taken off and a tax added on; and the price before a percentage was added is found by dividing, not by taking the percentage off again. Each has its own answer card on the page.
Further reading
Topics: how to calculate percentage · percentage of a number · what percent is · percentage formula · percent calculator · percentage calculator
A little less theory. A little more doing.
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