About
TheBuildingCode is a growing set of free, plain-English calculators and guides for the building trades — sizing tools, layout geometry, unit conversions, and the everyday math — built for the people who actually do the work, and for homeowners trying to get it right. It covers the United States, Canada, the United Kingdom, Australia and New Zealand, with each country getting its own pages, units and terminology.
Why we built it
The math behind trade work isn't secret, but it's scattered: half-remembered rules of thumb, formulas buried in code books, and online calculators that give you a number with no working behind it. We wanted the opposite — tools that answer the question you actually typed, instantly, and then show every step of how the answer was reached, so you can check it instead of trusting it.
How the tools work
Every calculator runs on published formulas and stated assumptions, with the working shown under the result. Where a building-code rule applies to a calculation, the tool names the code section and edition it used; where a value differs by country, each country's page uses its own. Long-standing rules of thumb (like stair comfort rules) are clearly labelled as guidance, never presented as legal requirements. The full method is on our How we calculate page.
What we add, and how often
We publish new calculators and guides continuously, choosing what to build next from what people actually search for — the most-asked questions get tools first. Each new calculator ships together with a plain-English guide explaining the method, a worked example, and answers to the questions people really ask about it.
What this site is not
It is not a substitute for your local code, your inspector, or a licensed professional where one is required. Building rules are adopted and amended locally, so the same calculation can have different legal limits in two neighbouring jurisdictions. Our job is to get you a correct, transparent number fast; checking that number against the rules in force where you are is always the last step, and it's yours.
Questions, corrections or tool requests? Use the contact page — corrections especially. If we got something wrong, we want to know quickly.
Everything here is reference only — not professional engineering or legal advice. Codes are adopted locally and change over time, so always confirm with your local Authority Having Jurisdiction (AHJ) before you start work.