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Stairs Calc

Riser height

The vertical height of a single step; every riser must be equal within 3⁄8 in.

Riser height (or unit rise) is the vertical height of one step — how far your foot lifts from one tread to the next. Building codes require every riser in a flight to be the same within 3⁄8 in (9.5 mm), because an odd step is a trip hazard. You never pick riser height directly; you divide the total rise by a whole number of risers. Example: 110 in of rise over 15 risers is 7.33 in (186 mm) each. The IRC caps residential risers at 7¾ in (197 mm); the IBC commercial limit is 7 in (178 mm). Taller risers make a steeper, more tiring climb.

Try the calculator Stair Rise and Run Calculator

Related terms

Total rise Vertical distance from the lower finished floor to the upper finished floor. Number of risers How many equal steps the flight has; total rise divided by target riser, rounded. Run (going) The horizontal depth of one step, measured nosing-to-nosing, not counting the overhang. Riser (board) The vertical board that closes the gap between two treads on a closed-riser stair.

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Stair Rise and Run Calculator Turn one total‑rise measurement into equal risers and runs that meet code — with the comfort rules (2R+T and Rise+Run) checked for you.
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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.