Percentage Calculator
Three everyday percentage problems, solved the instant you type.
What is X% of Y?
Result
30
X is what % of Y?
Result
20%
Percentage change from X to Y
Result
+20%
20% increase
Reverse: value after a % change
Original value before the change
150
How it works
Percent means "per hundred," so every percentage problem is just division and multiplication by 100:
- X% of Y = (X ÷ 100) × Y
- X is what % of Y = (X ÷ Y) × 100
- Percentage change = ((new − old) ÷ old) × 100 — positive means an increase, negative a decrease
- Reverse a change: original = final ÷ (1 + change ÷ 100)
Watch out for percentage points: a rate moving from 10% to 15% rose 5 percentage points, which is a 50% relative increase. They are not the same thing.
Frequently asked questions
How do I calculate a percent of a number?
Divide the percent by 100 to get a decimal, then multiply by the number. For example, 20% of 150 is 0.20 × 150 = 30.
What is the difference between percent and percentage points?
They measure different things. If a rate rises from 10% to 15%, that is a 5 percentage point increase — but a 50% relative increase. Mixing them up is one of the most common percentage mistakes.
How do you calculate percentage increase?
Subtract the old value from the new value, divide by the old value, and multiply by 100. For example, going from 150 to 180 is (180 − 150) ÷ 150 × 100 = 20% increase.
How do I work backwards from a percent change?
To reverse a change, divide instead of multiply. If a price after a 20% increase is 180, the original was 180 ÷ 1.20 = 150. Note that a 20% increase followed by a 20% decrease does not return to the start — it lands slightly lower.