Calculorium is an independent project that builds free online calculators and tools. There are currently 455 of them, grouped into 20 categories — finance, health, maths, conversion, timers, text and more.
What we are trying to do
Most calculator sites make you scroll past three paragraphs of filler to reach a box that adds two numbers. We build the opposite: the tool sits at the top of the page, gives an answer the moment you type, and the explanation underneath is there for people who want to check the maths or learn the formula — not to pad the page out.
How the tools are built
Every tool is a plain HTML page with the calculation written in vanilla JavaScript. There is no backend and no account system. Whatever you type stays in your browser and is never transmitted, stored or logged. That is a consequence of how the site is built, not a policy we could quietly change.
Before a calculator is published, its formula is run against worked examples in an automated test suite. If the numbers do not match the expected result, the page does not ship. Where a tool implements a named standard — Mifflin-St Jeor for BMR, the Devine formula for ideal weight, WCAG contrast ratios, the annuity formula for loan payments — that source is named on the page itself.
Corrections
If you find a result that looks wrong, tell us and we will check it. A calculator that quietly returns the wrong number is worse than no calculator at all, so corrections take priority over new tools. Email hello@calculorium.com.
How the site is funded
Calculorium is free to use and is funded by advertising. Ads never sit inside or above a calculator's input fields, and they never affect a result. See our methodology for the full picture of how tools are built and checked.