Percentage Calculator
Four ways to calculate percentages, all in one place. Find what X% of Y is, what percent X is of Y, the percentage increase or decrease between two values, and reverse percentages. Results update instantly as you type.
1. What is X% of Y?
2. X is what percent of Y?
3. Percentage Increase / Decrease
4. Reverse Percentage (X is Y% of what?)
Percentage Formulas
- X% of Y = (X ÷ 100) × Y
- X is what % of Y = (X ÷ Y) × 100
- Percentage change = ((New − Old) ÷ Old) × 100
- Reverse percentage = X ÷ (Y ÷ 100) = (X × 100) ÷ Y
Frequently Asked Questions
How do I calculate a percentage?
To find X% of Y, divide X by 100 and multiply by Y. For example, 20% of 250 = (20 ÷ 100) × 250 = 50. The first calculator above does this automatically.
What is the difference between percentage change and percentage point change?
Percentage change is relative to the original value. Percentage point change is an absolute difference between two percentages. If a rate goes from 5% to 7%, that is a 2 percentage point increase but a 40% increase in the rate itself.
Why can't I calculate a percentage change from zero?
Percentage change from zero is undefined because you cannot divide by zero. If the original value is zero, report the absolute change instead ("went from 0 to 500") rather than a percentage.
How do I calculate a reverse percentage?
If X is Y% of an unknown total, divide X by (Y ÷ 100). For example, if 50 is 25% of a total, the total is 50 ÷ 0.25 = 200. The fourth calculator above does this.
Can percentage change be negative?
Yes — a negative result means the value decreased. A result of −20% means the new value is 20% lower than the old value. The direction is indicated by the sign.
Is this calculator free to use?
Yes — completely free, no signup, no limits. Everything runs in your browser. No numbers you enter are sent to a server or stored.