Percent Calculator
Quickly work out any percentage — what is X% of a number, what percent one number is of another, and percentage change.
What is X% of Y?
Quick Reference
About the Percent Calculator
Percentages come up constantly — in shop discounts, exam scores, tips, interest, tax and statistics — yet they are easy to get wrong under pressure. A percent calculator removes the guesswork by handling the arithmetic for you and, just as importantly, showing the formula it used so you can check the logic and learn it for next time.
There is more than one kind of percent question, and they need different formulas. "What is 15% of 80?" multiplies a number by a rate. "12 is what percent of 50?" divides one number by another. "What is the percentage change from 40 to 52?" measures growth relative to a starting value. Mixing these up is the most common source of percentage mistakes; this calculator keeps them separate so you always apply the right one.
Use it for everyday tasks — checking that a sale price is really the discount advertised, splitting a bill, converting a test mark, or working out a markup — and for quick sanity checks when a figure someone quotes you "feels" off. It runs entirely in your browser and never stores anything you type.
Looking for more options? Open the full Percentage Calculator — it’s the same tool with every feature.
Frequently Asked Questions
How do I calculate a percentage of a number?
Multiply the number by the percentage expressed as a decimal. For example, 15% of 80 is 80 × 0.15 = 12. This calculator does it for you and displays the formula, so you can confirm the result and reuse the method.
How do I find what percent one number is of another?
Divide the first number by the second and multiply by 100. For example, 12 out of 50 is (12 ÷ 50) × 100 = 24%. Select that mode in the calculator and it shows both the answer and the working.
What is the difference between percentage points and percent?
A change from 20% to 25% is a rise of 5 percentage points, but a 25% increase in relative terms (5 ÷ 20). They are different measures and are often confused. Use the percentage-change mode for relative change, and simple subtraction for percentage-point differences.
Understanding Percentages
The three core percentage calculations
Almost every percentage question is one of three types. Finding a percentage of a number multiplies the number by the rate as a decimal (15% of 80 = 80 × 0.15). Finding what percent one number is of another divides the part by the whole and multiplies by 100 (12 of 50 = 24%). Finding percentage change divides the difference by the original value. Identifying which type you have is half the battle — the rest is arithmetic the calculator handles.
Converting between fractions, decimals and percentages
A percentage is just a fraction out of 100, so they convert freely. To turn a percentage into a decimal, divide by 100 (25% → 0.25); to go the other way, multiply by 100. A fraction becomes a percentage by dividing top by bottom and multiplying by 100 (3/4 → 75%). Being comfortable moving between these forms makes mental estimates easier and helps you sanity-check the calculator’s output.
Common percentage mistakes
The classic errors are applying a percentage to the wrong base, and assuming increases and decreases cancel out. A 20% rise followed by a 20% fall does not return you to the start, because the second percentage is taken from a larger number. Likewise, adding percentages from different totals is rarely valid. When a result feels surprising, re-checking which number the percentage is "of" usually reveals the issue.