Stair Calculator
Find the number of steps, riser height, total run, stringer length and angle for a straight stair, checked against the IRC limits.
Steps (risers)
14
- Riser height
- 7.5 in
- Treads
- 13
- Total run
- 130 in
- Stringer length (approx.)
- 167.108 in (13' 11 1/8")
- Stair angle
- 36.87°
- 2021 IRC riser/tread check
- Passes (riser ≤ 7¾ in, tread ≥ 10 in)
Checks only the 2021 IRC riser and tread limits (R311.7.5). Your local code, headroom, nosing and handrail rules still apply.
Show the work
Total rise ÷ maximum riser
rise ÷ max riser
105 ÷ 7.75 = 13.5483871
Round up to whole steps
risers = ⌈rise ÷ max riser⌉
⌈13.5483871⌉ = 14
How it works
Risers = ⌈total rise ÷ max riser⌉; riser = total rise ÷ risers; treads = risers − 1; run = treads × tread depth; stringer ≈ √(rise² + run²)
Questions
- How does the stair calculator work?
- Risers = ⌈total rise ÷ max riser⌉; riser = total rise ÷ risers; treads = risers − 1; run = treads × tread depth; stringer ≈ √(rise² + run²).
- What do I need to enter?
- Total rise (floor to floor), Maximum riser, Tread depth. Optional fields can be left blank.
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