Percentage Calculator

Multiply the number by the percentage, then divide by 100: (45 x 18) / 100 = $8.10. This calculation is behind discounts, tips, taxes, and interest - anywhere you are taking "a percentage of" something.

Divide the amount you are comparing by the total, then multiply by 100. If you saved $30 on a $200 jacket, that is (30 / 200) x 100 = 15%. This is the reverse of "what is X% of Y?" - here you already have both numbers and want the percentage itself.

Multiply the amount you know by 100, then divide by the percentage. If you saved $18 at 20% off, the original price was (18 x 100) / 20 = $90 - checkable in reverse, since 20% of $90 is indeed $18.

Percentage change measures how much a value grew or shrank compared to its own starting point - going from $50 to $42 is a -16% change, because you are comparing the change to $50. Percentage difference instead compares two values to each other, with neither one treated as the "starting" value, and usually divides by their average instead. These terms get used interchangeably a lot, but they can give genuinely different answers for the same two numbers.

A negative result just means the value went down - it is not an error. Going from $50 to $42 gives exactly -16%, correctly showing a decrease. Going the other way, from $42 back to $50, gives about +19.05% - a bigger-looking number for the "same" gap, because the calculation is always measured against wherever you started.

Yes. A percentage over 100% just means the part is bigger than the whole you are comparing it to - for example, 250 is 125% of 200. In percentage change terms, going from 10 to 25 is a 150% increase. There is nothing special about the 100% mark; it just means "equal to the whole" or "equal to where you started."

Yes, in every mode - the calculator does not block negative numbers anywhere. In "What is X% of Y?", finding a percentage of a negative amount is a valid calculation, like a negative account balance: 15% of -$200 is -$30. The other three modes will also compute a signed result if you enter a negative number, though their typical real-world use - discounts, test scores, comparisons - usually involves positive amounts.

Multiply a decimal by 100 to get a percentage (0.15 becomes 15%), or divide a fraction's top number by its bottom number and then multiply by 100 (3/20 becomes 0.15, then 15%). The "X is what % of Y?" mode does exactly this for you - enter 3 as the part and 20 as the whole, and it returns 15% directly.

They sound similar but mean different things. If an interest rate goes from 5% to 7%, that is a rise of 2 percentage points - but in relative terms, it is actually a 40% increase, since (7 - 5) / 5 x 100 = 40%, because 2 is 40% of the original 5. News and finance often say "percentage points" specifically to avoid this confusion, since "a 2% rise" and "a 2 percentage point rise" can mean very different amounts.

It depends on which piece is missing. If you know the discount amount and the original price, use "X is what % of Y?" to find the percentage - like $30 off a $200 jacket being 15% off. If instead you know the discount amount and the percentage but not the original price, use "X is Y% of what?" - like knowing you saved $18 at 20% off and finding that the original price was $90.

Yes - "What is X% of Y?" and "X is Y% of what?" work backward from each other within the same part-percentage-whole relationship. 15% of 200 is 30 - and if you instead know that 30 is 15% of some number, working backward through "X is Y% of what?" gives you 200 again. Whichever of the three numbers - the part, the percentage, or the whole - you do not know, one of the three modes solves for it.