This Percentage Calculator handles three everyday calculations: finding a percentage of a number, finding what percentage one number is of another, and measuring the percentage change between an original and a new value. Choose the calculation type and enter the two values to see the result.
How to use the Percentage Calculator
- Choose a calculation type from the list.
- Enter the requested first and second values. The field labels change to match the selected calculation.
- Select Calculate to display the result.
- Change the calculation type to solve another percentage problem.
Available percentage calculations
1. What is X% of Y?
Formula: (X ÷ 100) × Y. Example: 20% of 500 = (20 ÷ 100) × 500 = 100.
2. X is what percentage of Y?
Formula: (X ÷ Y) × 100. Example: 45 is what percentage of 180? (45 ÷ 180) × 100 = 25%. The whole value (Y) cannot be zero because division by zero is undefined.
3. Percentage change from X to Y
Formula: ((Y − X) ÷ X) × 100, where X is the original value and must be greater than zero. Example: a value rises from 80 to 100. The change is (20 ÷ 80) × 100 = 25% increase. A negative result represents a decrease.
Percentage change versus percentage points
A percentage change describes the relative change from an original value. A percentage-point change is the simple difference between two percentages. For example, moving from 10% to 12% is an increase of 2 percentage points, but a 20% relative increase. These are not interchangeable.
Frequently asked questions
How do I calculate a discount?
Use “What is X% of Y?” to calculate the discount amount, then subtract it from the original price.
Can the calculator handle decimals?
Yes. Enter decimal values where needed. The result is formatted for readability.
Why does a zero value cause an error?
The “X is what percentage of Y?” calculation divides by Y, and percentage change divides by the original value. A zero denominator makes those calculations undefined.
Calculations run in your browser; the values you enter are not submitted to Tooliday.