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Percentage Calculator
Three everyday percentage questions on one page. Pick the question you're asking, enter the two numbers, and the answer — with the working — updates as you type. The numbers are plain amounts, so this tool works the same in any currency.
What do you want to find?
Result
| Calculation | 80 × 20/100 |
| Result | 16 |
Percentages are unit-free: the answer is the same whether the amounts are dollars, hours, or anything else.
How the math works
Each mode is a different arrangement of the same idea — a percentage is a fraction out of 100:
In mode (c) a positive result is an increase and a negative result is a decrease. Note that the change is always measured against the starting value A — that's why going from 80 to 96 is +20%, but going back from 96 to 80 is −16.67%, not −20%.
Worked examples
One set of numbers, used all three ways:
(a) What is 20% of 80? → 80 × 20 ÷ 100 = 16
(b) 16 is what percent of 80? → 16 ÷ 80 × 100 = 20%
(c) From 80 to 96: → (96 − 80) ÷ 80 × 100 = +20% (an increase of 16).
Common gotchas
- Percentage points are not percent. If a rate rises from 5% to 7%, that's an increase of 2 percentage points — but a 40% relative increase. News reports mix these up constantly; mode (c) gives the relative change.
- Increases and decreases aren't symmetric. A 50% loss needs a 100% gain to recover, because the percentage is measured from the smaller, reduced base.
- Dividing by zero. "X is what % of 0" and "change from 0" have no answer — any amount divided by zero is undefined, and the calculator shows 0 rather than a misleading number.
- Percent of what? A "20% discount" then "another 10% off" is not 30% off the original: the second discount applies to the already-reduced price, for a combined 28% off.