Percentage Calculator
The three percentage questions everyone actually asks, answered instantly.
The three percentage formulas
X% of Y: multiply. (X ÷ 100) × Y. 15% of 240 is 36.
X is what % of Y: divide. (X ÷ Y) × 100. 36 is 15% of 240.
Percent change: (new - old) ÷ old × 100. From 240 to 276 is a 15% increase.
The trick that makes mental percentages easy
Percentages are commutative: X% of Y always equals Y% of X. 8% of 50 feels hard; 50% of 8 is obviously 4. Same answer. And build from 10%: to get 35%, take 10% three times plus half of 10%.
Percent change gotcha
A 50% drop needs a 100% gain to get back to even, because the base changes. That's also why a '50% increase then 50% decrease' leaves you 25% down, not at zero.