Percentage Calculator
Calculate a percentage of a number and percentage change.
About the Percentage Calculator
Percentages are useful for discounts, increases, comparisons, and everyday math. This calculator shows a percentage of a number and percentage change between an old and new value.
How to use this calculator
- Enter the percentage you want to calculate and the number it applies to.
- Enter an old value and a new value if you want percentage change.
- Review the percentage result and percentage-change result.
- Use the result to compare prices, quantities, rates, or other values.
How the calculation works
A percentage of a number is calculated as percentage ÷ 100 × number. Percentage change is calculated as (new value − old value) ÷ old value × 100, when the old value is not zero.
Example
20% of 85 is 17. If a value rises from 100 to 120, the percentage change is 20%.
Things to keep in mind
- Percentage change and percentage points are not the same thing.
- A negative percentage change means the new value is lower than the old value.
- Percentage change cannot be calculated normally from an old value of zero.
- Round results only after the calculation when precision matters.
Frequently asked questions
How do I find a percentage of a number?
Convert the percentage to a decimal and multiply it by the number.
How do I calculate percentage increase?
Subtract the old value from the new value, divide by the old value, and multiply by 100.
What is percentage change?
It measures how much a value has increased or decreased relative to its starting value.
What happens if the old value is zero?
Standard percentage-change math uses the old value as the denominator, so a normal percentage change is undefined when the starting value is zero.