Percentage
- Mode
- Of
- Meaning
- 15% of 80
About this percentage calculator
This page turns three common percent jobs into one form: find a percent of a number, reverse a percent, or measure percent change between two values. Pick the mode that matches the question you already have.
The math is plain arithmetic. Of = amount × percent ÷ 100. Reverse = part ÷ whole × 100. Change = (new − old) ÷ old × 100. Negatives and zeros are handled the same way a spreadsheet would — if the whole is zero, change is undefined and the page stays blank or shows a clear gap.
It is not a tax engine, tip splitter, or markup planner. Those have their own Bare tools. It also does not round for cash registers or currency rules beyond ordinary floating-point display.
How do I calculate a percentage?
Of: percent times the number, divided by 100. 15% of 80 is 12. Is %: the first number divided by the second, times 100. 12 is 15% of 80. Find whole: the first number divided by the percent over 100. 12 is 15% of 80.
Does this send my numbers anywhere?
No. The math runs in your browser. Nothing is uploaded or saved.
Can I copy the result?
Yes. Use the Copy button.
Nothing is stored. Runs in your browser.