Percentage Calculator
Pick one of four modes: what is X% of Y, X is what percent of Y, X is P% of what, or the percent change from an original value to a new one. The third mode is a reverse percentage calculator. It finds the whole from a part and its percentage, so 30 is 15% of 200. Enter the two numbers and press Calculate. The answer is rounded to 2 decimal places.
How to use the Percentage Calculator
- Enter your numbers in the Percentage Calculator above.
- Press the Calculate button to see the result.
- To try other numbers, change any value and press the button again.
The percentage formulas
X% of Y = (X / 100) × Y · · · X is what % of Y = (X / Y) × 100 · · · X is P% of W, so W = X / (P / 100) · · · Δ% = ((new − old) / old) × 100
Each mode runs one of these formulas. The calculator works with the numbers exactly as you type them and rounds once, at the end, so 15% of 3.3 shows 0.5 and not 0.49. In the second mode Y is the whole, so it cannot be 0. In the reverse mode P cannot be 0, because 0% of every number is 0. In Percent change the original value cannot be 0 either.
Worked example
What is 15% of 200? Answer: (15 / 100) × 200 = 30. What percent is 30 of 200? Answer: (30 / 200) × 100 = 15%. If a price rose from 200 to 230, the percentage change is ((230 − 200) / 200) × 100 = 15%, and the calculator shows 200 → 230 = +15% change. In reverse, 30 is 15% of what? Answer: 30 / (15 / 100) = 200, shown as 30 is 15% of 200.
Frequently asked questions
How do I calculate a percentage of a number?
Multiply the number by the percentage, then divide by 100. For example, 25% of 80 = (25 × 80) / 100 = 20.
How do I work out what percent one number is of another?
Divide the part by the whole and multiply by 100. For example, 18 out of 60 = (18 / 60) × 100 = 30%.
How do I calculate percentage increase or decrease?
Subtract the original from the new value, divide by the original, and multiply by 100. The calculator puts a plus sign on an increase and a minus sign on a decrease, so 80 to 60 shows -25% change.
How do I find the original number from a percentage?
Use the "X is P% of what?" mode, a reverse percentage calculation. It divides the part by the percentage and multiplies by 100. If 30 is 15% of a number, the number is 30 / 15 × 100 = 200. A price of 72 after a 20% discount is 80% of the original price, so the original was 72 / 80 × 100 = 90.
What is the difference between percentage points and percent?
A change from 10% to 12% is an increase of 2 percentage points, but a 20% increase in relative terms. Percent and percentage points measure different things and should not be used interchangeably.