This site exists because most online calculators give you a number and nothing else. A BMI figure with no mention of what it cannot see, or a mortgage payment with no note that it excludes tax and insurance, is a number that can quietly mislead you. We would rather show the formula, work an example, and say plainly where the method breaks down.
How the tools are built
Every calculator here runs entirely in your browser using plain JavaScript. Nothing you type is transmitted, logged or stored. There is no account to create and no data collected about what you calculate — closing the tab discards everything.
That is partly a privacy decision and partly a practical one. Salary figures, weights and loan amounts are the kind of thing people are reasonably cautious about typing into a website. Keeping the maths on your device removes the question entirely.
How we check the numbers
Each calculator implements a published, standard formula — Mifflin-St Jeor for metabolic rate, the standard amortisation formula for loans, the World Health Organization thresholds for BMI. The implementations are covered by automated tests that verify them against known reference values, so a change to one tool cannot silently break another.
Where a formula is contested or has well-known limitations, we say so on the page rather than burying it. That is the main thing that distinguishes these pages from a bare input box.
What we cover
The current tools span everyday mathematics, personal finance, health estimates and academic grading. Each page includes the formula written out, worked examples with real numbers, the mistakes people most often make, and answers to the questions that actually get asked.
Corrections
If a calculator returns something wrong, we want to know. Email contact@percentagecalculatorhub.com with the calculator, the values you entered and what you expected. Verified corrections are deployed quickly and we reply to say when.
How the site is funded
Advertising. The tools are free and we do not sell data — there is no data about your calculations to sell, since none of it reaches us. Our Privacy Policy sets out exactly what advertising cookies do and how to opt out.