Calculator
Percentage calculator
Calculate a percentage of a number, percentage ratio or percentage change. Data is processed only in your browser, and the page explains the formula and limitations of the result.
Reviewed: 3 August 2026Processed locally
Calculator
Enter data
A calculation mode and two numeric values A and B. Fields marked with an asterisk are required.
How to use the calculator
- Enter the required data: a calculation mode and two numeric values a and b.
- Check the values and select “Calculate”.
- Review the primary result and the detailed calculation components.
Calculation details
Formula and calculation method
A% of B = A ÷ 100 × B. Ratio = A ÷ B × 100%. Change = (B − A) ÷ |A| × 100%.
Worked example
20% of 150 is 30. The change from 150 to 180 is 20%, while 30 is 20% of 150.
Limitations
- Percentage change is undefined from a starting value of zero, and signed values affect interpretation.
Sources
Engine version: 1.0 · Last reviewed: 3 August 2026
Frequently asked questions
Is the entered data sent to a server?
No. The calculation runs locally in your browser and the values are not saved by default.
Is the result definitive?
Not always. Percentage change is undefined from a starting value of zero, and signed values affect interpretation.