Stair Stringer & Headroom Calculator

Turn floor-to-floor rise into a code-aware riser and tread layout. Compare IBC, IRC, and OSHA limits, then check total run, angle, and headroom before you cut stringers.

Stair Calculator

IBC / OSHA

1. Dimensions

Total Rise (Floor to Floor)

ft in

Building Code

Target Tread Depth

Upper Floor Thickness

2. Results

Laying Out Code-Compliant Stairs

Steel stair detailing starts with equal risers that fit the floor-to-floor height under the governing code. IBC commercial stairs typically max 7″ rise with 11″ minimum tread and 80″ headroom; IRC allows a slightly taller rise and shorter tread; OSHA industrial stairs allow steeper geometry (about 9.5″ rise/tread) within a 30–50° band. Total vertical rise over 12′ generally needs an intermediate landing.

How to use this calculator

Enter total rise in feet and inches (finish floor to finish floor, or to the landing elevation you are detailing).
Select IBC, IRC, or OSHA so maximum rise and minimum tread defaults update.
Set target tread depth and upper floor thickness for headroom, then Calculate Layout to get riser count, run, angle, and pass/fail checks.

Stringer and headroom notes

Keep riser heights equal within code tolerances — a 3/16″ variation between adjacent risers is a common field punch list. Headroom is measured plumb to the soffit along the nosing line; thick concrete-filled pans or deep landings steal clearance fast. Guard and handrail geometry, tread nosings, and stringer size are separate detailing tasks once the geometry clears.

FAQ

Do I include the top landing as a tread?

Riser count equals the number of vertical steps. The top landing is not an additional tread in the run length, but you still need landing depth per code at the top and bottom.

Which code applies to a plant mezzanine stair?

Often OSHA for employee access, sometimes IBC if the stair is part of the means of egress. Confirm with the AHJ and project specification — do not assume.

Why enter upper floor thickness?

It affects the headroom check under the landing or floor above. Ignoring slab/joist depth is how stairs pass rise/run but fail clearance.

Can I use this for spiral or alternating tread stairs?

No. Those systems have different dimensional rules. This tool targets straight flight stringer stairs.