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Tools / Percentage calculator

Percentage calculator

What is X% of Y, X is what percent of Y, and the percentage change from X to Y — all from two numbers. Divide-by-zero cases say so plainly instead of printing Infinity or NaN.

Runs entirely in your browser

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About this tool

Percentages come up constantly, but the phrasing varies, so this tool answers the three questions people actually ask, all from two numbers: what is X% of Y, X is what percent of Y, and what is the percentage change from X to Y. Between them these cover discounts, tips, tax, grades, growth figures and most other everyday percentage maths.

It also behaves sensibly at the edges. Where a calculation would divide by zero — asking what percent something is of nothing, for instance — it says so plainly rather than printing Infinity or NaN, which is confusing and easy to misread.

The maths runs in your browser, so answers are instant and nothing you type is uploaded. It is a fast, unambiguous reference for the kind of percentage question that is quick to get slightly wrong in your head.

Frequently asked questions

What percentage questions can it answer?
Three: what is X% of Y, X is what percent of Y, and the percentage change from one value to another. Together these cover most everyday percentage calculations.
How do I calculate a percentage increase or decrease?
Use the percentage-change option with the original and new values; it reports the change as a percentage, positive for an increase and negative for a decrease.
What happens if I divide by zero?
The tool states that the result is undefined rather than showing Infinity or NaN, so you are not misled by a meaningless number.
Can I use it for discounts and tips?
Yes — “what is X% of Y” gives a discount or tip amount directly, though the dedicated discount and tip tools add extras like stacking and bill-splitting.
Is the calculation private?
Yes. It runs in your browser, so the numbers you enter are not sent anywhere.

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