About Calc Dragon

Calc Dragon is a library of plain-spoken calculators for the questions people actually type into a search box. We build tools that give you the right number — with enough explanation that you understand where it came from.

What we build

Every calculator on this site starts with a real question — the kind that people search for dozens of times a day: how much should I be saving?, what does this interest rate actually cost me?, how many calories did I burn? We pick the ones where the maths is well-defined, implement the correct formula, write plain-language explanations of how it works, and publish it with enough context that the result is genuinely useful rather than just a number.

We currently have over 140 calculators across finance, health, maths, science, construction, and everyday topics — and new ones are added most weeks. If there is a calculation you keep doing by hand that belongs here, let us know.

Our quality bar

A calculator that gives you the wrong answer is worse than no calculator at all. Before anything goes live on Calc Dragon it has to pass an automated test suite that checks the formula against worked examples from authoritative sources — textbooks, official government guidance, or peer-reviewed standards. The tests run on every deployment. If they fail, nothing ships.

Each calculator page also includes a worked example — real numbers walked through step by step — so you can check the logic against your own calculation rather than having to trust a black box.

What our calculators are (and aren't)

Every calculator on Calc Dragon is an educational tool. They are designed to help you understand a calculation and get a sensible ballpark number. They are not professional advice. Before you act on any output — especially anything involving money, health, safety, or legal decisions — check the result with a qualified professional and with up-to-date official sources. Tax rates change, medical guidelines change, building codes vary by jurisdiction. Our calculators simplify; reality is more complicated.

The Learn section

Most calculators on the site have a companion guide in the Learn section. These are longer-form explanations of the topic itself — not just how to use the tool, but why the formula exists, where it comes from, and what the result means. If you want to understand the underlying maths rather than just get the number, start there.

Contact

Questions, corrections, suggestions, or spotted a bug in the maths? Email hello@calcdragon.com. We read everything, even if the reply is slow.