About PercentageHQ

What is PercentageHQ?

PercentageHQ is a free online percentage calculator that covers eight types of calculation in one place: finding what X% of a number is, working out what percentage one number is of another, calculating percentage change or difference, adding or subtracting a percentage, running a reverse percentage to find an original value, and calculating a percentage of a percentage.

Results update in real time as you type, and every answer includes a plain English explanation of how it was calculated — so you can follow the working, not just read a number.

Who built it?

PercentageHQ is built and maintained by Rose Venture Labs, a New Zealand-based venture builder focused on simple, useful digital tools. The goal was straightforward: build the best free percentage calculator available — one that covers every common calculation type, explains its working clearly and gets out of the way.

Are the calculations accurate?

Yes. Every calculator uses the standard mathematical formula for its calculation type. Percentage change uses the original value as the denominator. Percentage difference uses the average of both values. Reverse percentage divides by the decimal form of the percentage. These are the same formulas used in school maths, financial analysis and scientific research worldwide.

All calculations run in your browser using JavaScript floating-point arithmetic, with results rounded to 8 significant figures to avoid rounding artefacts. There are no external API calls and no server-side processing — the result is computed entirely on your device.

Why is it free?

Good basic tools shouldn't cost anything. PercentageHQ is designed to be supported by advertising, which keeps it free to use without paywalls, sign-ups or tracking of what you calculate.

Who uses it?

Anyone who needs a quick, reliable percentage calculation — which is a lot of people. Students checking exam scores, shoppers comparing discounts, business owners applying VAT or a markup, employees verifying a pay rise, analysts calculating percentage change between two data points. The calculator is designed to be fast and obvious enough to get an answer in a few seconds without reading any instructions.

Does PercentageHQ collect my data?

No. Nothing you type into the calculators is ever sent to us or any third party. All calculations happen entirely in your browser. We use Google Analytics to understand general site usage — page views, session duration, approximate location — but no personally identifying information is collected, and your calculations are completely private. See our Privacy Policy for the full details.