Bullnose step
A rounded starting step, wider than the flight, that wraps past the newel.
A bullnose is a starting step whose end is curved into a quarter- or half-round, projecting wider than the rest of the flight so it sweeps past the newel post at the bottom. It gives a staircase a softer, more welcoming entry and a natural place to begin the balustrade curve. Example: a 36 in (914 mm) wide flight might sit on a bullnose first tread that bulges to 44 in (1118 mm) so the volute handrail scroll can land over the rounded end. Code treats it like any other step — the riser height and walkline run must still meet the limits — but the flared shape is purely a styling choice. A double bullnose rounds both ends for a free-standing open stair.
Related terms
Stair calculators
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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.