🪜Stair Calculator
Work out the number of steps, riser height, tread depth and stringer length for your stairs.
Your stairs
You'll need
14 steps
Riser 7.71 in · tread 11.54 in · stringer 184.84 in
📏 Building codes vary. Always check these results against your local code before you cut or build.
riser height
7.71 in
tread depth
11.54 in
treads
13
stringer length
184.84 in
🛒 Shopping list
- Stringer boards (2×12, 16 ft)3 boards
- Stair treads13 treads
- Riser boards14 boards
Keep every riser the same height — even a small difference is a trip hazard.
How it works
Risers = total rise ÷ 7.75 in, rounded up. Riser height = total rise ÷ risers. Treads = risers − 1, and tread depth = available run ÷ treads. Stringer = √(rise² + run²).
Building codes vary. Always check your results against your local code.
Worked example
A 108 in rise with 150 in of run:
- 108 ÷ 7.75 = 13.9 → 14 steps, each 7.71 in tall
- 13 treads, 150 ÷ 13 = 11.54 in deep
- √(108² + 150²) = 184.8 in stringer (buy 16 ft boards)
Questions people ask
Many US codes allow up to 7¾ in, but check your local rules.
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Last updated September 28, 2026. These results are friendly estimates to help you plan — always double-check before buying or making big decisions.