About Stairs Calc
Stairs Calc exists to make code‑compliant stair planning effortless — free, transparent, and accurate, with every formula and code citation shown.
Our mission
Stairs Calc exists to make code-compliant stair planning effortless. Most stair calculators give you a number; we give you a complete, checked plan — the steps, the exact riser, the stringer to cut, a 3D model, and a live check against the building code that applies to your project — for free, with no sign-up.
We built the tools we wished existed: an instant answer on first paint, transparent formulas and cited code sections you can verify, a beautiful 3D diagram that turns red the moment a dimension breaks code, and one-tap sharing, printing and PDF export. Every page is a genuinely different working tool, never a doorway.
Read exactly how the numbers are produced on our methodology page, or browse the stair code requirements the tools enforce.
Start with the stairs calculator
Written by the Stairs Calc editorial team. Methodology and code references: see our methodology.
Built and maintained by builders, drafters and engineers who plan stairs for a living — every code limit is transcribed from the published standard and cited to its exact section.
Last reviewed 2026-06-20 against IRC 2021/2024
Stairs Calc gives accurate geometry and checks it against published building-code limits, but results are estimates for planning. Codes are adopted and amended locally and change over time. Always confirm dimensions against your local adopted code and a licensed professional before you build.