Percent of a Number Calculator

This answers the three percentage questions people actually ask, all at once, because they are easy to confuse with each other. What is 15 percent of 200? That is a share of a whole, and the answer is 30. What percentage is 15 of 200? That is a different question with a different answer, 7.5 percent, and mixing the two up is the single most common percentage error. What is 200 plus 15 percent? That is 230, and it is what you need for adding GST, a markup or a service charge. All three are on this page together so you can see which one you meant. Two things worth knowing while you are here. Adding a percentage and then removing the same percentage does not return you to where you started: 200 plus 15 percent is 230, but 230 less 15 percent is 195.50, not 200, because the second percentage is taken from a larger number. And a percentage of a percentage multiplies rather than adds, so two successive 10 percent discounts give 19 percent off, not 20. Both catch people out in real money.

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%
30
is 15% of 200
Number plus that percent230
Number minus that percent170
15 as a percent of 2007.5%
Add then remove the percent195.5
Percent as a decimal0.15

Adding a percentage and then removing the same one does not return the original number, because the second is taken from a larger base.

How it works

A percentage of a number is the number multiplied by the percentage divided by 100. Adding a percentage multiplies by one plus that fraction, and subtracting multiplies by one minus it. The reverse question, what percentage one number is of another, divides the first by the second and multiplies by 100. The add-then-remove line demonstrates why the two operations are not inverses: the removal is calculated from the increased figure, not the original.

Worked example

Take 15 percent of 200, the defaults. Fifteen divided by 100 is 0.15, and 200 x 0.15 is 30. Adding that gives 230 and subtracting it gives 170. Reversing the question, 15 as a percentage of 200 is 15 divided by 200 times 100, which is 7.5 percent, a completely different answer to the same two numbers. Now add 15 percent to 200 and take 15 percent off the result: 230 less 15 percent is 195.50, which is 4.50 short of where you started.

Related calculators

Data sources: arithmetic only; no external figures are used.

Frequently asked questions

How do I find a percentage of a number?

Multiply the number by the percentage and divide by 100. So 15 percent of 200 is 200 times 15 divided by 100, which is 30. Alternatively convert the percentage to a decimal, 0.15, and multiply.

What percentage is one number of another?

Divide the first by the second and multiply by 100. So 15 is 7.5 percent of 200. This is a different question from finding 15 percent of 200, which is 30, and confusing the two is the most common percentage mistake.

Why does adding then removing a percentage not return the original?

Because the second calculation uses a larger base. Adding 15 percent to 200 gives 230, and 15 percent of 230 is 34.50 rather than 30, so removing it leaves 195.50. The same effect means two successive 10 percent discounts total 19 percent, not 20.