Skip to content
Stairs Calc

Headroom

Vertical clearance measured plumb above the nosing line; minimum 6 ft 8 in (IRC).

Headroom is the vertical clearance above the staircase, measured straight up from the nosing line to the ceiling, soffit, or stairwell edge above. Too little and tall users hit their heads on the stairwell opening framing. The IRC and IBC both require a minimum of 6 ft 8 in (2032 mm) measured at every point along the flight. Example: if your floor structure is 12 in deep, the rough opening must start far enough back along the run that the diagonal headroom never drops below 80 in. Spiral stairs get a reduced 6 ft 6 in (1982 mm) allowance. Check headroom at the worst point — usually where the stair passes under the upper floor.

Try the calculator Stairs Calculator

Related terms

Stairwell opening The hole framed in the upper floor that the staircase rises through. Nosing The lip of the tread that overhangs the riser below; ¾–1¼ in in the IRC. Spiral staircase A helical stair whose wedge treads wind around a central column. Stair soffit The finished underside of a staircase or its landing.

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.