Percentage Calculator
Find a percent of a number, what percent one number is of another, and percent change.
A percentage is a part of 100. To find X% of a number, multiply the number by X and divide by 100; 15% of 200 is 30. To find what percent one number is of another, divide the part by the whole and multiply by 100. To find a percent change, divide the difference by the original value. This calculator does all three.
Results are estimates provided for general information.
What is A% of B?
30
A is what percent of B?
15%
Percent change from A to B
50%
About the Percentage Calculator
Percentages turn a fraction into a value out of 100, which makes different quantities easy to compare. This calculator covers the three questions people ask most. The first finds a part of a whole: X% of Y, done by multiplying Y by X and dividing by 100. The second works backward, telling you what percent one number is of another by dividing the part by the whole. The third measures change between two numbers, the difference divided by the starting value, which is how you read a price increase or a test-score improvement. One case trips people up: a change from zero has no percentage, because there is nothing to compare against, so it is left blank rather than shown as infinity. Percentages also do not simply add. A 20% rise followed by a 20% fall does not return you to the start, since the second percentage is taken from a larger number.
Frequently asked questions
How do I calculate a percentage of a number?+
Multiply the number by the percent and divide by 100. For 15% of 200, that is 200 × 15 ÷ 100 = 30.
How do I find what percent one number is of another?+
Divide the part by the whole and multiply by 100. 30 out of 200 is 30 ÷ 200 × 100 = 15%.
How do I calculate percentage change?+
Subtract the old value from the new value, divide by the old value, and multiply by 100. Going from 100 to 150 is a 50% increase.
Why can't I calculate a percent change from zero?+
Percent change compares the difference to the starting value, and dividing by zero is undefined. A change from 0 to any number has no meaningful percentage.
Do percentages add together?+
No. A 20% increase followed by a 20% decrease leaves you below where you started, because each percentage is applied to a different base amount.