The Percentage Calculator solves the three percentage questions people ask most often: what is X percent of a number, one number is what percent of another, and the percentage increase or decrease between two values. Type your numbers, pick the calculation, and the answer appears instantly along with the exact formula used to reach it.
Percentages trip people up because each question uses a different formula. Finding a tip means multiplying by a percent, working out a discount rate means dividing, and measuring growth means comparing a change against the original amount. This tool keeps the three operations separate and clearly labeled so you always apply the right one — no memorizing formulas, no spreadsheet, no mental arithmetic.
Every calculation runs entirely in your browser. Nothing you type is sent to a server, the tool works offline once the page has loaded, and there is no signup or usage friction. Results are rounded to four decimal places to stay readable while avoiding the floating-point rounding noise that plain JavaScript math often produces.
Select one of three modes: "What is X% of Y", "X is what % of Y", or "Increase / decrease" for percentage change between two numbers.
Type a value into each field. The labels change to match the selected mode so you always know which number goes where.
The answer appears as a plain-English sentence with the numeric result and the formula that produced it, so you can verify or reuse the math.
Copy the result to your clipboard for a document, invoice, or message, or change the numbers to run another calculation instantly.
Percent of a number, one value as a percent of another, and percentage increase or decrease — the three questions that cover almost every everyday percentage task
Each result includes the exact arithmetic used, so you can check the math or learn how the calculation works
Change mode automatically labels the result as an increase, decrease, or no change and reports the magnitude clearly
Results are rounded to four decimals and formatted with thousands separators, avoiding the long floating-point tails raw JavaScript math produces
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