Wood Stair Calculator
Design comfortable stairs that feel right underfoot. Enter the floor-to-floor height and available run, and get riser height, tread depth, slope and stringer length — with clear safety limits.
Workshop AI assistant
Describe the piece you want to build and get a complete plan: dimensions, cut list, materials, cost, steps, tools and time.
Workshop assistant
Describe the piece you want to build and get a complete plan: dimensions, cut list, materials, cost, steps, tools and time.
AI-generated results are indicative. Verify dimensions, loads and local codes before building.
How it works
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1
Enter the total rise (floor-to-floor height) and the available run (horizontal length).
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2
Optionally set the tread thickness, stair type and landing constraints.
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3
Calculate: the tool rounds to an ideal riser, then derives treads, slope and stringer.
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4
Check the warnings — values outside comfort ranges are flagged.
Formula
Riser = total rise / number of steps. Comfort rule (Blondel): 2 × riser + tread = 63 cm (±3 cm). Slope = atan(rise run / run). Development = number × √(riser² + tread²). Stringer length ≈ √(total rise² + run²).
Practical tips
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Keep risers between 15 and 18 cm and treads between 26 and 32 cm for comfort.
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Aim for 2 × riser + tread close to 63 cm — it matches the natural walking stride.
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Add one nosing of 2–3 cm to the tread depth when measuring usable depth.
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Never skip the local code check: minimum widths and maximum risers are regulated.
Common mistakes
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Mixing rise and run: the run is horizontal, the rise is vertical.
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A staircase that is comfortable on paper but has an opening (trémie) too small.
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Ignoring headroom clearance above the stairs.
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Uniform risers everywhere except one — that single step causes trips.
Disclaimer
These results are indicative only. Always verify against local building codes, standards and professional advice before building.
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