Solve the most common percentage questions in one place: a percent of a number, what percent one number is of another, percent change, and adding or taking off a percentage.
Pick the question you want to answer, then fill A and B. The text of each option tells you what A and B mean.
Formulas and assumptions
- A percent of B: A divided by 100, times B
- A is what percent of B: A divided by B, times 100
- Percent change: (new minus old) divided by old, times 100
- Increase B by A percent: B times (1 + A divided by 100)
- Decrease B by A percent: B times (1 minus A divided by 100)
Example
20 percent of 150 is 30. A change from 80 to 100 is a 25 percent increase, and 30 is 20 percent of 150.
Frequently asked questions
How do I calculate a percentage of a number?
Divide the percentage by 100 and multiply by the number. 20 percent of 150 is 0.20 times 150, which is 30.
How do I find percent change?
Subtract the old value from the new one, divide by the old value and multiply by 100. A positive result is an increase and a negative one is a decrease.
Why is a 50 percent rise followed by a 50 percent fall not back to the start?
The second change is applied to a bigger number. 100 up 50 percent is 150, and 150 down 50 percent is 75.
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