Free online calculators, with the formula shown.

No. Calculations run in your browser and nothing you type leaves the page — not your salary, not your loan balance, not your weight. A few tools fetch a live price (gold, currency) from a named third party, and that request sends nothing about you. Full detail in our privacy policy.

No, and there isn’t one to make. Every calculator is fully usable the moment the page loads — no sign-up, no email, no trial, no feature held back behind a login. If a site asks you to register before showing you a number, it is selling something other than the number.

Because the maths runs on your device rather than a server. Once a page has loaded, it keeps working with no connection — useful on a building site, in a basement, or on a plane. The only exceptions are tools that need a live market price, which will tell you plainly when they cannot reach it.

So you can check the answer instead of trusting it. Every tool shows the working with your own figures substituted, plus a worked example. If a result looks wrong, you can see exactly which step produced it — which also means you learn something, rather than just collecting a number.

Each tool uses the standard formula for its field. Where an answer is genuinely an estimate, we say how wide the estimate is rather than implying a precision we don’t have — a building cost worked out from floor area could be 25% out in either direction, and pretending otherwise would be the more convincing lie. For money, health or legal decisions, treat any result as a starting point and confirm it with someone qualified.

Anything that moves is either pulled live or left for you to edit. The gold calculator fetches the current spot price and shows how fresh the reading is. The building cost estimator starts from a current average but lets you type in a local figure — because a price baked into a website goes out of date quietly, and you would never know. Where we quote a published benchmark, we say which year it is from.

Yes. Most tools print cleanly to paper or PDF, and copy as plain text with the figures, the method and the date included — ready to paste into a document or attach to a quote. Some also export a CSV of the full working, such as a loan schedule or a set of statistics.

The mortgage calculator for the full monthly payment including tax, insurance and PMI, and the month your PMI drops off. The affordability calculator if you are still working out what you can borrow. The refinance calculator if you already have a loan and want to know whether switching covers its own closing costs.

Not inside the tool itself. Nothing sits between you and your result, and nothing covers the screen while you are typing. Advertising, where it appears, sits around the content, and any link that earns us a commission is marked as such before you click it.