Percentage Calculator
Four percentage tools in one: find a percent of a number, increase or decrease a value by a percent, work out what percent one number is of another, and reverse a percentage to recover the original number.
How to use Percentage Calculator
- Pick the calculation: Percent of, Increase / decrease, What percent of, or Reverse.
- Type the two numbers — the live sentence above the result shows exactly what is being computed.
- Read the result instantly; nothing is sent anywhere, all math runs in your browser.
Frequently asked questions
- How do I find X% of a number?
- Use the "Percent of" mode: X% of Y = (X ÷ 100) × Y. For example, 15% of 200 is 30.
- How is a percentage increase or decrease calculated?
- In "Increase / decrease" mode the change amount is value × percent ÷ 100. That amount is added for an increase and subtracted for a decrease, so both results are shown side by side.
- What does the reverse mode do?
- It answers "this number is X% of what?" by dividing the number by the percentage as a fraction — e.g. 30 is 15% of 200. It is handy for removing tax or a markup to find the original price.
- Is my data uploaded anywhere?
- No — the calculator is pure JavaScript that runs entirely on your device.