About GintiCalc

What GintiCalc is

Close to 600 calculators across twelve categories — finance, math, health and fitness, converters, business, developer tools, education, travel, automotive, home and DIY, science, and sports. Every page does exactly one job: you enter numbers, you get an answer, and directly underneath you get the arithmetic that produced it — the formula, your values substituted into it, and each intermediate result on its own line.

That last part is why the site exists. Most calculator pages hand you a figure and nothing else. If the figure looks wrong, you have no way to tell whether you mistyped an input, misread the question, or hit a bug in someone else's JavaScript. Showing the working turns a black box into something you can check, disagree with, and learn from.

How a calculator is built, and how the numbers are checked

Every formula on this site lives in a plain TypeScript function with no user-interface code wrapped around it — loan amortisation in one file, basal metabolic rate in another, unit conversions in a third. Those functions take numbers and return numbers, and that is all they do. They can be read, reasoned about, and tested on their own.

Each of them has a matching explainer function, and the explainer never re-derives the answer. It calls the same plain function, takes the result it gets back, and narrates the steps around it. That is a deliberate constraint. On a lot of sites the displayed working and the displayed answer come from two different pieces of code, which is exactly how you end up with steps that quietly disagree with the total. Here they cannot disagree, because there is only ever one calculation.

Those functions are then covered by a unit-test suite of more than a thousand cases. The tests check results against worked examples, against the standard definition of each formula, and against the explainer output, so a step that drifts away from the number it claims to produce fails the build rather than reaching a page. Where a calculation has an accepted standard — Mifflin–St Jeor for resting metabolic rate, European Central Bank reference rates for currency, ordinary amortisation for loans — the site uses that standard, and the notes on each calculator page name the formula so you can check it against a source that isn't me.

What this site does not do

There are no accounts and no sign-up, because no calculator here needs one. Nothing you type is stored, and there is no profile sitting behind any of the tools.

The calculations run in your browser. With one exception, no network request happens while you calculate: the currency converter fetches the day's reference exchange rates, and that request only pulls rates down — your amounts are never sent anywhere. The layout is built around the calculator rather than around advertising, so the tool you came for is the first thing on the screen.

Results here are educational. They are good enough to plan with and good enough to sanity-check a number someone else gave you, but they are not financial, medical, tax, or legal advice, and I am not licensed to give any of those. A calculator only knows the handful of values you typed into it. Before you act on a number that genuinely matters, check it with a professional who knows the rest of your situation.

Corrections and contact

If a calculator gives you a result you believe is wrong, please tell me — that is the most useful message this site can receive. Send the inputs you used, the result you got, and the result you expected. Because each formula lives in a single tested function, a real error is usually a small fix plus a new test case that stops it coming back.

The same address works for anything else: a calculator you wish existed, a formula variant used where you live, a page that renders badly, or a question about how a number was arrived at.