Percentage calculator
Calculate percentages in your browser: what percent X is of Y, X percent of a value, and percent change between two numbers. Free and private — nothing is uploaded.
About this tool
Three percentage questions cover most everyday needs, and this calculator answers each of them with its formula shown rather than just a bare number: what percent one value is of another, what a given percent of a value comes to, and the percent change between two values. It is the tool for discount checks, tax and tip arithmetic, grade calculations and quick sanity checks on a spreadsheet.
Decimals are fully supported and results are rounded to six decimal places for display. Percent change needs a non-zero starting value because it divides by it, and everyday modes here work with non-negative inputs. Every calculation runs in this page — nothing you type is uploaded anywhere.
How to use Percentage calculator
- Choose one of the three percentage modes.
- Enter the two values. Decimals are supported.
- Run the calculation and read the result together with its formula.
Keep the original files and inspect the exported result before publishing or sharing it.
Frequently asked questions
What do the three modes calculate?
"What percent of" answers "X is what percent of Y?" (for example, 50 is 25% of 200). "Percent of value" answers "what is X% of Y?" (for example, 20% of 150 is 30). "Percent change" answers "from A to B, how many percent up or down?" (for example, 50 to 75 is a 50% increase).
Can I use decimals and large numbers?
Yes. Decimals are fully supported and results are rounded to six decimal places for display. Extremely large values above 10^15 are rejected as unrealistic.
Why does percent change fail when the first value is zero?
Percent change divides by the starting value, and division by zero is undefined. Enter a starting value greater than zero.
Why are negative numbers rejected?
These modes are designed for everyday percentage questions with non-negative values. A decrease still shows as a negative percent change, for example 200 to 150 is −25%.
Is my input uploaded anywhere?
No. Every calculation runs locally in your browser. Nothing you type leaves this page.
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