About TudoCalc

TudoCalc started from a common irritation: searching for "net salary calculator" and landing on a page that spits out a number without explaining where it came from, surrounded by ads that jump around while you read. The idea here is the opposite — show the working, not just the result.

The site now holds 201 calculators, 44 guides and 23 interactive lessons, in English and Portuguese, covering finance, health, maths, physics, chemistry, construction, cooking, dates and unit conversion.

Who makes it

The project is created and maintained by Rafael Rossi, a software developer. There is no outsourced writing and no bought text: every calculator, guide and lesson is written, checked and tested by the same person who signs the site. When a reader reports an error, that is the person who answers and fixes it.

How a calculator gets made

Every page follows the same process, and that is what separates TudoCalc from a formula aggregator:

1. The formula comes from the source. BMI ranges from the WHO; conversion factors from the International System of Units; tax tables from the legislation in force. On health, finance and tax topics, the sources are listed on the page itself.
2. The numbers are checked before publishing. Every worked example you read was calculated and verified — long tables included. A page's text once contradicted its own calculator over a rounding rule; that is now checked for.
3. The page explains. An explicit formula, a step-by-step example with real numbers, and FAQs that answer what people actually ask — not decorative filler.
4. The date is visible. Each page shows when it was reviewed and which reference year it uses. Rules change; an honest site keeps that in plain sight.

The area-by-area detail is on the methodology and sources page.

The interactive lessons

This is the part we are proudest of and the part that exists nowhere else. Each interactive lesson opens with a mini-game that exposes the intuition almost everyone gets wrong — what percentage of your first mortgage payment is interest? is the "fat-burning zone" real? — continues with a simulator you drive with sliders, and ends with the counter-intuitive lesson the numbers reveal. There are 23 of them, covering 80 of the site's calculators.

Our principles

• Free, no sign-up. No calculator asks for a login, an email or a payment.
• Real privacy. Calculations run in your browser — salary, weight and debt are never sent to any server. That is architecture, not a promise.
• Restrained ads. The site is supported by advertising, but never with pop-ups, full-screen interstitials, autoplay sound, or a block that shoves the text while you read.
• Honesty about limits. Calculators are estimates. Where the subject is serious — blood alcohol, fertile window, roof structure — the page states outright what it is not good enough to decide.

Why it's free

Because charging for a three-line calculation would be absurd. Running the site costs little (it is static, with no application server) and advertising covers the rest. If that ever changes, the change will be announced here — not hidden behind a usage limit.

Get in touch

Found a calculation error? Missing a calculator? The contact page explains what to include so the fix ships fast. Reader corrections are the best thing that lands in the inbox.

Disclaimer: the calculators are informational and educational. Health results do not replace medical assessment, and financial, employment or tax results do not replace an accountant's, lawyer's or adviser's guidance. See the Terms of Use.