Percentage calculator

Percentages trip people up because the same word covers a few different questions. This tool keeps them separate, so you pick what you mean and get a clean answer.

The three modes

• % of — a slice of a number. 15% of 80 is 12.
• is what % — how big one number is next to another. 12 is 15% of 80.
• % change — how much something rose or fell. 80 to 100 is a 25% increase; 100 to 80 is a 20% drop.

Why the direction matters

A 25% rise followed by a 25% fall does not return you to the start — the second percentage is taken from a bigger number. The change mode makes that asymmetry obvious, which is handy for prices, tips, and discounts.

Worked examples

Say an $80 jacket is marked 15% off. In % of mode, 15% of 80 is 12, so you save $12 and pay $68. To check a tip instead, switch to is what %: a $12 tip on an $80 bill works out to 15%. And if a stock moves from $80 to $100, % change shows a 25% gain — yet the same $20 move back from $100 to $80 is only a 20% loss, because the starting number is larger. Lining the three up side by side is the quickest way to see which question you actually have.

Everyday uses

Most percentage questions in daily life fall into one of the three modes once you spot the pattern.

• Sales tax. Adding 8% tax to a $50 purchase: 8% of 50 is 4, so the total is $54. The one-step shortcut is to multiply by 1.08, which gives the same $54.
• Tips. An 18% tip on a $47.50 dinner is $8.55 in % of mode. If you would rather round the tip to a clean number, you can check afterward what percent it came to using is what %.
• Test scores. Scoring 42 out of 60 on an exam is a question for is what %: 42 is 70% of 60.
• Pay raises. A jump from $52,000 to $55,000 is a 5.77% raise in % change mode — useful when an offer states the new salary but not the percentage. Whether that raise actually beats inflation is its own question — the raise vs inflation guide runs the real-dollars math.

The increase-then-decrease trap

A percentage increase and a same-sized percentage decrease do not cancel out. Start with $100 and add 25%: you get $125. Now take 25% off that $125 and you land on $93.75, not $100. The reason is that the 25% decrease is measured against the larger $125, so it removes more dollars than the increase added. This shows up with investment returns (a 50% loss needs a 100% gain to break even), with discounts, and with anything quoted as a swing up and back down.

The same logic explains why stacked discounts disappoint. A coupon for 30% off followed by an extra 20% off is not 50% off. The second cut applies to the already-reduced price, so $100 becomes $70 and then $56 — a real discount of 44%, not 50. When you compare the two paths, the single 50%-off price of $50 still wins. The stacked discounts guide walks through why the advertised total is almost always bigger than the discount you get.

Percent versus percentage points

These two are easy to mix up and the gap can be large. If an interest rate or a poll number moves from 10% to 12%, that is a rise of 2 percentage points — a plain subtraction. But in relative terms it is a 20% increase, because 2 is a fifth of the starting 10. Headlines often blur the two, so it is worth checking which one a figure actually means before you act on it.

Frequently asked questions

Last reviewed June 2026.