Percentage Calculator

Four percentage questions answered, with the working shown.

%
3015% of 200
The other part
170
Working
200 x 15 / 100 = 30

About the Percentage Calculator

Percentages come up constantly and the four questions people ask about them are always the same: what is a percentage of a number, what percentage is one number of another, how much has something changed in percentage terms, and what happens when you add or take off a percentage. This calculator answers all four and prints the arithmetic underneath, so you can copy the working into homework or a spreadsheet.

The percentage-change mode is the one that trips people up. Going from 120 to 150 is a 25 percent increase, but going back from 150 to 120 is a 20 percent decrease, because the base changes. The same asymmetry explains why a price that rises 50 percent needs a 33 percent cut to return to where it started.

How to use the Percentage Calculator

  1. Pick the type of percentage question you want to answer.
  2. Fill in the two numbers. Only the fields that matter for the chosen question are shown.
  3. Read the answer and the working line underneath, which shows the formula with your numbers in it.

Frequently asked questions

How do I calculate a percentage of a number?

Divide the percentage by 100 and multiply by the number. Fifteen percent of 200 is 0.15 x 200 = 30. The first mode of this calculator does exactly that.

What is the difference between percentage change and percentage points?

If a rate rises from 4 percent to 6 percent, that is a rise of 2 percentage points but a 50 percent increase. News reports mix the two often, so it is worth checking which one is meant.

How do I reverse a percentage increase?

Divide by 1 plus the percentage as a decimal. A price of 120 that already includes a 20 percent markup started at 120 / 1.2 = 100. Subtracting 20 percent from 120 gives 96, which is the wrong answer.

Why is a percentage decrease not the same size as the increase?

Because each is measured against a different starting value. A rise from 100 to 150 is 50 percent of 100, while the fall from 150 back to 100 is 33.3 percent of 150.