How to use the percentage calculator
- Pick the question you are asking: What is X% of Y, X is what percent of Y or X is Y% of what number.
- Fill in the two numbers shown. Decimals and negative numbers are fine.
- Read the answer. The steps show the formula with your numbers.
Formula
X% of Y = (X / 100) x Y
X is what percent of Y = (X / Y) x 100
X is Y% of what = X / (Y / 100)
A percent is a fraction of 100. 15% means 15 out of 100, or 0.15.
Worked examples
15% of 80: 0.15 x 80 = 12.
12 is what percent of 80: 12 / 80 = 0.15, and 0.15 x 100 = 15%.
12 is 15% of what: 12 / 0.15 = 80.
A percent above 100 works the same way: 150% of 40 is 1.5 x 40 = 60.
Quick mental math
Find 10 percent by moving the decimal one place left: 10% of 80 is 8. Then build the rest: 5% is half of that, so 15% of 80 is 8 + 4 = 12. 1% is two places left, 25% is a quarter and 50% is half.
Percent of, percent change and percentage points
Going from 20% to 25% is a 5 percentage point increase but a 25 percent increase in the rate. For a change between two values use the percent change calculator.
Real-life uses
Work out a tip, a discount, a sales tax amount, a test score, a salary increase or what share of a budget goes to rent. For the common pricing cases there are dedicated tools: discount, sales tax and tip.
Assumptions and limits
- The whole in "what percent" cannot be zero, and the percent in "what number" cannot be zero. Those questions have no answer, so the tool explains instead of showing infinity.
- Answers are shown to up to 6 decimal places.
- Percent signs and commas are accepted in the number boxes and removed before calculating.
Frequently asked questions
How do I calculate a percentage of a number?
Divide the percent by 100 and multiply by the number. 20% of 350 is 0.20 x 350 = 70.
How do I take a percent off a price?
Multiply the price by 1 minus the discount. 25% off $120 is $120 x 0.75 = $90. The discount calculator also stacks discounts and adds tax.
How do I turn a fraction into a percent?
Divide the top by the bottom and multiply by 100. 3/8 is 0.375, so 37.5%.