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About Percentage Calculator Online
This tool handles the three most common percentage questions: "what is X% of Y?", "X is what percent of Y?", and "what is the percentage change from X to Y?". Each calculation has its own input fields and the result is shown instantly.
Percentage calculations come up everywhere: tips, taxes, discounts, grade scores, statistical comparisons, business growth, and population changes. Having a tool that handles all three common variants in one place avoids the easy errors that come from doing the math in your head.
The percentage-change calculation correctly distinguishes increases from decreases and shows the signed result. Useful when comparing year-over-year revenue, exam scores, weight loss, or any other before-and-after comparison.
How to use this tool
How to compute the three classic percentage problems
Choose the mode
"Mode" picks the problem: `of` ("X% of Y is …?"), `whatPercent` ("X is what % of Y?"), or `change` ("% change from X to Y"). Each one takes the same two number inputs but treats them differently.
Enter A and B
"Value A" and "Value B" are the two operands. In `of` mode A is the percent and B is the base. In `whatPercent` A is the part and B the whole. In `change` A is the old value and B the new — negative results mean a decrease.
Press Run
Result returns a single `result` field. `of` returns `A × B / 100`. `whatPercent` returns `A / B × 100`. `change` returns `(B − A) / A × 100`. All rounded to 2 decimals.
Sanity checks
Increase from 100 to 150 is +50% (change mode). 50 is 25% of 200 (whatPercent). 30% of 80 is 24 (of). Anything that doesn't match those intuitions is probably the wrong mode for what you meant to ask.