Calculator Tools
Calculate a percentage of a value, determine what percentage one number is of another, or measure percentage change.
Calculation type
Input
Simple workflow
How to use Percentage Calculator
- 1Choose the percentage question that matches your calculation.
- 2Enter both values using the field labels for that question.
- 3Select the calculation button and read the result and explanation.
Good to know
Frequently asked questions
How do I calculate a percentage of a number?
Choose What is X% of Y?, enter the percentage and the value, then select Find percentage of value. For example, enter 25 and 200 to get 50: (25 ÷ 100) × 200 = 50.
How do I find what percentage one number is of another?
Choose X is what percent of Y?, enter Part and Total, then select Find percentage. For example, 50 out of 200 is 25%: (50 ÷ 200) × 100 = 25%. Total must not be zero.
Why is going from 80 to 100 a 25% increase, but going back a 20% decrease?
Each calculation uses its own starting value. The increase is 20 ÷ 80 × 100 = 25%, while the decrease is −20 ÷ 100 × 100 = −20%. Swapping the inputs changes the base of the calculation.
Can the original value be zero or negative for percentage change?
Zero is not supported as the original value because it would require division by zero. Negative original values are supported using their absolute value as the denominator: (new − original) ÷ |original| × 100.
What is the difference between percent change and percentage points?
Going from 20% to 30% adds 10 percentage points. Relative to the starting 20%, that is a 50% increase. Enter 20 and 30 in percent-change mode to calculate the relative increase.
Practical guide
Choose the percentage question that matches your numbers
Use What is X% of Y? to find an amount: 25% of 200 is 50. Use X is what percent of Y? to express a part of a total: 50 out of 200 is 25%. The first question returns a number; the second returns a percentage.
What is the percent change? compares Original value with New value. For positive starting values, it divides the difference by the original value and multiplies by 100. The result includes a signed percentage and an increase or decrease explanation.
Worked example
Measure a change from 80 to 100
- Start with
- The original value is 80 and the new value is 100.
- Choose
- Choose What is the percent change?, enter those values in Original value and New value, then select Find percentage change.
- You get
- The result is 25%, described as a 25% increase. Reversing the values to 100 and 80 gives −20%, a 20% decrease.
Tips for a useful result
- Total cannot be zero when finding a part's percentage, and Original value cannot be zero when finding percentage change. For a negative original value, this calculator divides by its absolute value.
- A change from 20% to 30% is 10 percentage points, but a 50% relative increase. Entering 20 and 30 in percent-change mode returns the relative increase.
- Displayed results round to at most six decimal places. Changing either value clears the previous result. Select the calculation button to get the updated result before using Copy result.
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