Percentage Calculator

Calculate percentages, reverse percentages, and percent change.

What is X% of Y?

Enter a value for all required fields.

About this calculator

Use this calculator to find a percentage of a number, reverse a percentage, or measure percent change between two values.

How to use

  1. Choose a calculation mode.
  2. Enter the required numbers.
  3. The result updates automatically.
  4. Use Reset to clear the inputs, or Copy to copy the result.

Formula

X% of Y = (X ÷ 100) × Y
X is what % of Y = (X ÷ Y) × 100
Percent change = ((New − Original) ÷ Original) × 100

Example

20% of 150 = 30
25 is what percent of 200 = 12.5%
From 100 to 120 = 20% increase

FAQ

How do I calculate a percentage of a number?

Divide the percentage by 100, then multiply by the value. Example: 20% of 150 = 0.2 × 150 = 30.

What if the whole or original value is zero?

Division by zero is not allowed. The calculator shows an error instead of an invalid result.

Can I calculate percent decrease?

Yes. Use the percent change mode and enter the original and new values. A lower new value shows a decrease.

Results are for informational purposes only. Verify important calculations independently.