Stair Calculator
Lay out a code-compliant staircase: riser count and height, tread depth, total run, stringer length, and angle — with IRC R311.7 limits checked as you type.
Formula and figures last reviewed by the Cosyslabs team · how we verify
Inputs
Result
Risers
14
Riser height
7.71 in
Treads
13
- Total run
- 130 in (10.8 ft)
- Stringer length
- 14.1 ft
- Stair angle
- 39.7°
- Tread stock needed
- 39.0 linear ft
- 2 × riser + tread = 25.4 in; the comfort rule targets 24–25 in.
Estimates only. Verify with a licensed contractor or supplier before purchasing. Rough Estimator! is not responsible for shortages, overages, or material variances. See our methodology for formulas and sources.
Formula
Risers = round(total rise ÷ target riser) · Riser height = total rise ÷ risers · Treads = risers − 1 · Stringer = √(rise² + run²)
References
Related tools & materials
Don't forget
- Stringer stock (2×12)
- Tread boards
- Riser boards
- Handrail
- Joist hangers
- Structural screws
Also useful
Frequently asked questions
Divide the total rise by your target riser height and round to the nearest whole number — that is your riser count. Then divide the total rise by that count to get the exact riser height. The rise never changes; the number of risers is what you adjust.
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Cosyslabs. (2026). Stair Calculator. Rough Estimator!. https://roughestimator.com/stair-calculator
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