Stair calculator

15 risers of 7-1/4"14 treads of 10-1/2"

Risers: 15 × 7-1/4"
Treads: 14 × 10-1/2"
Total run: 12' 3"
Stringer (floor-to-floor diagonal): 15' 3"
Angle: 34.7°

These sketches are here to help you order material and price the work quickly. They are not engineered or shop drawings — always build from your approved project drawings.

Total rise (floor to floor)Tread depthStair width

Number of risers

Auto picks the fewest equal risers at or under 7¾". IRC limits: risers ≤ 7¾", treads ≥ 10", headroom ≥ 6' 8", width ≥ 36". Check your local code.

Show the math▾

Number of risers
n = ⌈total rise ÷ 7¾"⌉
⌈ 9' 1" ÷ 7-3/4" ⌉ = 15
Riser height
total rise ÷ risers
9' 1" ÷ 15 = 7-1/4"
Treads
risers − 1 (the top step is the floor)
15 − 1 = 14
Total run
treads × tread depth
14 × 10-1/2" = 12' 3"
Stringer (floor-to-floor diagonal)
√(rise² + run²)
√( 9' 1" ² + 12' 3" ²) = 15' 3"

Where the numbers come from

Residential stair limits (IRC R311.7): Riser ≤ 7¾" · tread ≥ 10" · headroom ≥ 6' 8" · width ≥ 36"IRC 2018/2021 R311.7.1, .2, .5.1, .5.2, as published in building-department stair guides (Town of Timnath; Placer County). Risers in a flight may differ by no more than ⅜", and so may treads. Some places still use older editions — check your local code.Source

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Equal risers from the total rise, treads, run and stringer — flagged when they break the residential code.