Percentage Calculator
Find percentages, percent change, and reverse percentage values.
About this tool
Percentage Calculator handles the three percentage problems people reach for a calculator most often: finding what X% of a number is (useful for discounts, tax, tips, and grades), calculating how much something changed as a percentage (price rises, growth rates, score comparisons), and working backwards to find the whole when you know a part and its rate. Switch between the three modes with one tap, enter your numbers, and the answer appears instantly — no submit button needed. Everything runs in your browser; nothing is sent anywhere.
How to use
- Pick the type of calculation you need — '% of number', '% change', or 'Reverse %'.
- Enter the values in the input fields.
- The result updates instantly as you type.
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FAQ
What are the three modes?
'% of number' finds X% of Y. '% change' shows how much a value increased or decreased between two numbers. 'Reverse %' tells you what the original whole was when you know the part and the percentage.
How do I calculate a discount?
Use '% of number'. Enter the discount rate as X and the original price as Y — the result is the discount amount. Subtract it from the original price to get the final price.
How is percent change calculated?
Percent change = ((New − Old) ÷ Old) × 100. A positive result means an increase; a negative result means a decrease.
Is the calculation done in the browser?
Yes. Everything runs locally in your browser. No data is sent anywhere.
What is the 'Reverse %' mode for?
It answers questions like 'if 50 is 25% of something, what is that something?' — useful when you know the part and the rate but need the whole.