About the Percentage Calculator
The FreeToolr Percentage Calculator answers the three percentage questions people ask most: what is X% of a number, what percent one number is of another, and how much a value has gone up or down. Shoppers use it for discounts and sales tax, students for homework and exam marks, and small business owners for margins and price changes. It uses the standard formulas shown below, rounds to four decimal places and runs entirely in your browser, so the numbers you type are never sent anywhere. You can copy the answer, download it, or share a link that reopens the calculator with your numbers.
How to use it
- 1Pick what you want to find: percent of a number, what percent, or percent change.
- 2Type your two numbers. The answer updates as you type.
- 3Copy the result or save it to your workspace.
Worked example
A jacket costs $80 and is 15% off. 15% of 80 is 12, so you save $12 and pay $68. If the price later rises from $68 to $85, that is a 25% increase.
The formula
Percent of: result = x * p / 100What percent: p = x / y * 100Percent change: (new - old) / |old| * 100Source: Khan Academy: Percent word problems. Last checked 31 October 2026.
What it is good for
- Three common percentage questions in one place
- Shows the formula so you can check the math
- Works offline once loaded
- For compound growth over many periods, use the compound interest calculator instead
Questions people ask
How do I calculate a percentage of a number?
Multiply the number by the percentage, then divide by 100. For example, 20% of 150 is 150 x 20 / 100 = 30.
How do I work out percent increase?
Subtract the old value from the new value, divide by the old value, then multiply by 100. Going from 50 to 65 is (65 - 50) / 50 x 100 = 30%.
What percent is 30 of 120?
Divide 30 by 120 and multiply by 100. The answer is 25%.
Can a percent change be more than 100%?
Yes. If a value more than doubles, the increase is over 100%. Going from 40 to 100 is a 150% increase.
Is my data saved?
No. The math runs in your browser and nothing is sent to our servers unless you choose to save a result to your account.