Calculate percentages, ratios, and percent change online
What is the Percentage Calculator?
The percentage works like this: it solves the three classic percentage problems in one form: what is X% of Y, X is what percent of Y, and the percent change between two values. Everything happens on your device - the input never leaves your tab unless the tool clearly states it performs a server-side lookup.
How to use the Percentage Calculator
Enter the values the calculator asks for.
Double-check the unit or period next to each field (per month vs per year, cm vs m).
Read the result together with the breakdown shown beneath it.
Adjust one input at a time to compare scenarios side by side.
Features
Calculate percentages, ratios, and percent change online
Instant result, no page reload
Works in any modern browser, desktop or mobile
Free with no signup
Common mistakes to avoid
Mixing units or periods between fields
Rounding inputs before the final calculation
Treating estimates as guarantees for major decisions
Examples
Input
Result
From 80 to 95
Change: +18.75% increase
Best used for
Calculating discounts, sale prices, and tax
Figuring out tip percentages and gratuities
Comparing two prices or values (percent change)
Working out test scores or grade percentages
Privacy
Calculations run in your browser. Enter only what the calculation needs.
Frequently asked questions
Why is percentage increase not the same as decrease in reverse?
A 50% increase followed by a 50% decrease does not return to the start: 100 to 150 to 75. Percentages apply to different bases.
How do I add two percentages?
You cannot add them directly - apply sequentially (a 10% then 20% rise is 1.1 × 1.2 = 32%, not 30%).
Which of the three modes should I pick?
Use "X% of Y" for discounts and taxes, "X is what % of Y" for share-of-total questions, and "percent change" only when both numbers are amounts of the same thing at different times.
Why does a 100% increase followed by a 50% decrease return to the start?
Because the second percentage applies to the new, larger base: 100 to 200 to 100. The tool always shows which number each percentage acts on.
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