Online calculators that show their working

Yes, and free in the sense people usually mean: no account, no email address, no trial that expires and no result held back for a paid tier. Every calculator on this site opens and works immediately. There is no advertising on the pages either, and — unusually for a site with a loan calculator on it — no "compare offers" button, because we do not pass anyone to lenders. This is a directory, not a lead generator, and the calculators are cheap to run because the work happens in your browser rather than on our servers.

No. All five calculators are JavaScript that runs on your device — the salary you type into the budget planner, the debt in the loan calculator and the weight in the BMI tool are never transmitted to us, never stored and never logged. You can verify this by opening your browser's network tab and watching that nothing is sent while you calculate. It is why the calculators need JavaScript on: a server-side version would have to receive your financial and health data first, which is exactly what we are avoiding.

Named ones, and each tool says which. Loan repayments use the standard annuity formula, run month by month so the schedule shows real interest rather than an average. Percentages and VAT use ordinary arithmetic, but applied to the correct base — removing VAT divides rather than subtracting. Calories use the Mifflin-St Jeor equation, today's usual choice for non-clinical estimates. BMI is weight divided by height squared. If a calculator will not tell you what it used, you cannot check its answer, and that is a reason to distrust it rather than a detail.

Use them to understand the shape of a decision, not to make it alone. The loan calculator will show you honestly what an extra 100 a month does to a 25-year mortgage, which is genuinely useful before a meeting — but your lender's figure will differ because an APR folds in fees we cannot know about. The calorie estimate carries about a 10 per cent margin between individuals. The BMI number is a screening ratio and not a diagnosis. Everything here is information; the decision, and the document that governs it, are yours.

Use the "list your project" form. Tell us what it calculates in a sentence, who it is for, and which subdomain you would like. We look at four things: it must be usable without an account, it should show its working rather than emitting a single unexplained number, it must not hand the user to a lender or advertiser at the moment they get their result, and it must work on a phone. Listing is free, there is no exclusivity, and we translate your card into all twelve languages. We reply either way, including when the answer is no.

Twelve: English, German, Spanish, French, Hindi, Indonesian, Italian, Dutch, Polish, Portuguese, Swedish and Turkish. That covers the whole site, not just the front page — every calculator label, every option in every dropdown, every result sentence and every guide. Currency and number formatting follow the language you choose, so a thousands separator looks the way you expect it to. The language switcher keeps you on the page you were reading, and your choice is remembered in your browser without a cookie banner, because it never leaves your device.