Skip to content
Stairs Calc

Nosing

The lip of the tread that overhangs the riser below; ¾–1¼ in in the IRC.

The nosing is the rounded or square lip where the tread overhangs the riser beneath it. It gives your foot extra landing depth without lengthening the whole staircase, and the rounded edge is gentler on toes and shins. The IRC requires a nosing of ¾ in to 1¼ in (19–32 mm) when the tread run is less than 11 in, and the projection must not vary more than 3⁄8 in between treads. Example: an 11 in (279 mm) tread with a 1 in nosing gives a 10 in run. Open-riser and full-11-in-run stairs may omit the nosing. Over-deep nosings catch heels, so codes cap it.

Try the calculator Stairs Calculator

Related terms

Tread The horizontal board you step on; its depth equals the run plus the nosing. Riser (board) The vertical board that closes the gap between two treads on a closed-riser stair. Run (going) The horizontal depth of one step, measured nosing-to-nosing, not counting the overhang. Nosing return The mitred end-cap that finishes an open-side tread nosing flush with the skirt.

Stair calculators

Use this term in a calculator

Stairs Calculator Enter one measurement — your total rise — and get a complete, code‑compliant stair layout with a 3D diagram, stringer cut list, and printable template. Free, instant, in inches or millimeters.
All stair terms

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.