Percentage Calculator
Find a percentage of a number, a percentage relationship, or percent change.
Covers the three percentage calculations people actually need: what X% of a number is, what percent one number is of another, and the percent increase or decrease between two numbers. Pick a mode, enter the two values, and the result updates instantly. All math runs locally in your browser.
Runs on your device. This tool processes your file inside this browser tab. Nothing is uploaded, so it also works offline once the page has loaded, and closing the tab discards the file from memory.
Loading tool
How it works
- 01
Choose a calculation mode.
- 02
Enter the two numbers.
- 03
Read the result, updated as you type.
Details
- Category
- Developer & data
- Runs
- In your browser
- Files uploaded
- No
- Cost per run
- Free
- Sign-in
- Not required
- Works offline
- Yes, once loaded
Last updated 2026-08-12
Common questions
How is percent change calculated?
((Y - X) / X) * 100, using the starting value X as the base. A negative result means a decrease.
What if I divide by zero?
The 'is what %' and 'percent change' modes need a non-zero base value; the result is left blank if the base is 0.
Use this from your code
This tool is also a REST endpoint, so you can run it in a pipeline instead of by hand. It is free and needs no API key. See the API reference for every parameter.
curl -X POST https://fileoven.com/api/v1/tools/percentage-calculator \
-H "Content-Type: application/json" \
-d '{"mode":"of","x":20,"y":50}'