“Percentage problem” covers at least four genuinely different questions, and picking the wrong one is where most wrong answers actually come from, not the arithmetic itself.
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Percentage Calculator
Every common percentage question in one place, with the formula shown for each.
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The four percentage questions, side by side
% of a number answers "what is 25% of 80?" (20). What percent answers "15 is what percent of 60?" (25%). % change answers "going from 50 to 60, what's the percentage change?" (a 20% increase). Increase/decrease answers "what is 80 increased by 25%?" (100). They're four different questions that all get called "percentage problems", picking the wrong one is the most common source of a wrong answer.
Percentage calculator FAQ
How do I calculate a percentage of a number?
Divide the percentage by 100, then multiply by the number. 25% of 80 is (25÷100)×80 = 20. The "% of a number" mode above does this for any two values instantly.
How do I find what percent one number is of another?
Divide the part by the whole, then multiply by 100. If 15 out of 60 students passed, that's (15÷60)×100 = 25%. Use the "what percent" mode with 15 as the part and 60 as the whole.
What is the difference between percentage change and percentage points?
Percentage change is relative: going from 50% to 60% is a 20% increase (10 ÷ 50 × 100). Percentage points is the raw difference: the same move is "a 10 percentage point increase." Mixing these up is one of the most common errors in reading statistics, and they can differ by a lot when the starting number is small.
Why is a 20% increase followed by a 20% decrease not back to the original number?
Because each percentage applies to a different base. Increasing 100 by 20% gives 120, but decreasing 120 by 20% gives 96, not 100, since 20% of 120 is more than 20% of 100. The "increase/decrease by %" mode shows this directly: try it both ways on the same starting number.
Is this calculator private?
Yes. Every calculation runs in your browser. Nothing you enter is sent to a server, logged, or stored.
Free percentage calculator by ANUPRESS
Four questions, four formulas
“What is 25% of 80?” divides the percent by 100 and multiplies. “15 is what percent of 60?” divides the part by the whole and multiplies by 100. “What’s the percentage change from 50 to 60?” divides the difference by the starting value. “What is 80 increased by 25%?” multiplies by (1 + the percentage). Four different operations, and every one of them gets called a “percentage calculation” in casual conversation, which is exactly why picking the right mode above matters more than getting the multiplication right.
Percentage points are not percent
A survey moving from 40% approval to 44% approval increased by 4 percentage points, but that’s a 10% relative increase (4 ÷ 40 × 100). Financial and political reporting mixes these up constantly, sometimes accidentally, sometimes to make a change sound bigger or smaller than it is. When a headline says a rate “rose by 5%”, check whether they mean 5 percentage points or a genuine 5% relative increase, they tell very different stories from the same starting number.
Why a discount and a markup don’t cancel out
Increase a price by 20% and then decrease the new price by 20%, and you don’t land back where you started. €100 increased by 20% is €120; €120 decreased by 20% is €96, not €100, because the second 20% is calculated against a bigger number. This shows up constantly in retail (a “50% off” sale after a “50% markup” doesn’t return to the original price) and in investing (a 50% loss needs a 100% gain to recover, not another 50%). The increase/decrease mode above lets you check this directly on any numbers.