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Stair Layout for a 120 in Rise
16 risers · 15 treads.
Stair Layout for a 120 in Rise
StepsRiser 7.5 in · total run 150 in (12.5 ft)
Stringer length
16.01 ft
Angle
38.7°
Comfort (2R + T)
25 in (ideal 24–25)
Headroom needed
≥ 6 ft 8 in
IRC R311.7: max riser 7¾ in, min tread 10 in, riser variation ≤ ⅜ in, headroom 6 ft 8 in. Check local codes; commercial stairs are stricter (7 in / 11 in).
Planning estimates only. Building codes, loads and material specs vary — have a licensed engineer or contractor confirm quantities and safety requirements. Disclaimer
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