Stair Calculator
Lay out a straight stair using total rise, a chosen maximum riser and horizontal going.
Formula
N = max(2, ceil(total rise/max riser)); actual riser = rise/N; run = (N−1) × going.
Total floor-to-floor rise: 108 in · Chosen maximum riser height: 7 in · Horizontal going: 11 in · Number of risers ≈ max(2,ceil((108 in × 0.0254 m/in)÷(7 in × 0.0254 m/in)-8.881784197001252e-16×max(1,abs((108 in × 0.0254 m/in)÷(7 in × 0.0254 m/in))))) · Number of separate treads ≈ (16)-1 · Actual riser height ≈ (108 in × 0.0254 m/in)÷(16)×100 · Total horizontal run ≈ (15)×(11 in × 0.0254 m/in) · Step slope angle ≈ atan((108 in × 0.0254 m/in)÷(16)÷(11 in × 0.0254 m/in))×180÷pi
How to use
- Enter floor-to-floor rise and your chosen maximum riser.
- Enter horizontal going between successive nosings.
- Read risers, treads and run; upper floor is the final landing.
Examples
- A 280 cm rise with 20 cm maximum risers and 25 cm going needs 14 risers and 3.25 m run.
Frequently asked questions
Why is there one fewer tread?
The upper floor acts as the final landing, so N risers have N−1 separate treads.
Does going include the nosing overhang?
No. Going is horizontal spacing between successive nosings, not total board depth.
Is the result a compliant stair design?
No. Defaults are examples. Headroom, landings, width, guards and local requirements need separate checks.
Sources
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