Percentage Calculator
Percentages show up everywhere — discounts, tips, taxes, salary raises. This calculator handles the three most common percentage questions: what X% of a number is, what percentage one number is of another, and how much a number changed in percentage terms.
Percentage
Calculate X% of Y, reverse percentages, and percentage change instantly.
FAQs
How do I calculate percentage increase?
Use the % CHANGE mode: enter the old value and the new value, and the calculator shows the change as a percentage. A result of +15% means the number grew by 15%.
What is a reverse percentage?
It's finding the original number when you know the percentage and the result — for example, "I paid $110 after 10% tax; what was the original price?" Enter the result in X IS WHAT % OF Y mode, or simply divide $110 by 1.10 to get $100.
How it works
The calculator has three modes. X% OF Y answers questions like "how much is 8% sales tax on a $100 item?" — the answer is $8. X IS WHAT % OF Y works in reverse: "I paid $45 on a $180 bill — what percent was that?" Answer: 25%.
The third mode, % CHANGE, measures growth or decline between two numbers. If a portfolio grows from $2,000 to $2,300, that's a +15% change; if a price drops from $2,300 to $2,000, that's about −13.04%. Note that a rise and a fall by the same dollar amount are not the same percentage — the base they divide by is different.
Use the $/123 toggle to switch between money formatting (with currency symbols and commas) and plain numbers for grades, statistics, or anything else. The calculator guards against divide-by-zero, so you'll never get a nonsense result from a zero base.
The Everyday Math That Saves You Money
Discounts, tips, and taxes all run on percentages, and doing them mentally keeps you from being fooled by marketing. A "$50 off" sign on a $400 item is 12.5% off — the same $50 on a $200 item is 25%. The dollar figure is identical; the deal is not.
Tipping is the same skill in reverse: 20% on a $65 bill is $13, and knowing that instantly beats fumbling with your phone while the server waits. Percentage fluency is small math with outsized daily value.
Percentages in Salary and Price Negotiations
A "3% raise" on a $60,000 salary is $1,800 a year — about $150 a month. Framing raises, rent increases, and fee changes as dollar amounts makes them concrete in a way percentages never are.
The same trick works when you're selling: quoting a price increase as "$12 more per month" lands very differently than "a 15% increase," even though they're identical. Whichever side of the table you're on, convert the percentage to dollars before you decide how to feel about it.
Why Percentage Points Are Not Percents
When an interest rate moves from 5% to 7%, that's a 2-percentage-point increase — but a 40% relative increase in the rate itself. News headlines often blur this distinction, and it matters: "loan rates up 40%" sounds catastrophic, while "rates up 2 points" sounds mild. Both describe the same change.
Whenever you see a percentage about a percentage, slow down and ask which base it's measured against. That single question cuts through most statistical spin you'll ever meet.