Stringer
The notched board that carries the treads and risers; usually a 2×12.
A stringer is the inclined structural board, cut in a sawtooth pattern, that supports every tread and riser. Most residential stairs use 2×12 lumber so that enough solid wood — the throat — remains behind each notch. The number you need depends on width and tread thickness: a 36 in stair typically uses three. Example: for 14 risers, the stringer length is the hypotenuse of the total rise and total run, roughly 12 ft of stock. Codes do not give a stringer table, but a notched stringer must keep at least 3½ in (89 mm) of throat for adequate strength. Cut them from straight, dry, knot-free stock.
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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.