Percentage Calculator
Find a percentage of a number, express one value as a percentage of another, apply an increase or decrease, or calculate the change between two values.
Percentage of amount
Increase and Decrease apply the entered rate to the starting amount. Percentage change uses the original magnitude as its baseline and requires a nonzero original value. Values entered here are nonnegative.
Formula checked · NumberSwift · Review process
How this calculator works
Choose the operation that matches the question. Percent of finds a portion; What percent expresses a part relative to a whole. Increase and Decrease apply a known rate to a starting amount. Percentage change instead finds the rate between an original and new value. The original value or whole must be nonzero when it is the denominator.
Formula
Percent of: p × amount / 100. What percent: part / whole × 100. Increase or decrease: amount × (1 ± p/100). Percentage change: (new − original) / |original| × 100.
Assumptions & limitations
Increase and Decrease apply the entered rate to the starting amount. Percentage change uses the original magnitude as its baseline and requires a nonzero original value. Values entered here are nonnegative.
Sources & reference material
- OpenStax: understanding percent ↗
Reference for percentages and decimal proportions.
Worked example
What is 20% of 150? Convert 20% to 0.20 and multiply by 150 to get 30. To reverse the question, 30 ÷ 150 × 100 = 20%. Increasing 150 by 20% gives 180; decreasing it by 20% gives 120.
For a dedicated original-to-new comparison, the Percentage Change Calculator shows both the absolute difference and relative change.
Choose the right percentage calculation
| Question | Mode | Example |
|---|---|---|
| What is X% of Y? | Percent of | 20% of 150 = 30 |
| X is what percent of Y? | What percent | 30 out of 150 = 20% |
| Add X% to Y | Increase | 150 increased by 20% = 180 |
| Take X% off Y | Decrease | 150 decreased by 20% = 120 |
| How much did a value change? | Percentage change | 80 to 100 = +25%; 100 to 80 = −20% |
Common questions
What is the difference between Percent of and What percent?
Percent of finds a portion of an amount. What percent compares the first amount with the second and expresses that ratio per hundred.
Does a 20% decrease followed by a 20% increase cancel out?
No. Starting at 100, a decrease gives 80 and the subsequent increase gives 96 because the baseline changes.
How do I find the percentage increase or decrease between two values?
Choose Percentage change and enter the original value followed by the new value. From 80 to 100 the change is +25%; from 100 to 80 it is −20%. Increase and Decrease instead apply a percentage you already know.
Are percentage points the same as percentage change?
No. A rate moving from 10% to 12% rises by 2 percentage points, but the relative increase is (12 − 10) / 10 × 100 = 20%.