Precast Stair Design Calculator
Calculate precast stair dimensions, riser/tread count, stringer length, and weight from floor-to-floor height per IBC code.
Inputs
ft
in
in
in
pcf
Results
Total risers
22
Risers per flight11
Actual riser height6.55 in
Treads per flight10
Run per flight9.17 ft
Stringer length10.96 ft
Stair slope angle33.2°
Estimated weight9,043 lbs
Plan length12.83 ft
Comfort index (2R+T)24.09 in
Total Treads20
Comfort OkYes
Riser OkYes
Tread OkYes
Width OkYes
How to Use This Calculator
- Enter the floor-to-floor height in ft and the clear stair width in inches (IBC minimum 44 in for >50 occupants).
- Set the maximum riser height in inches (IBC max 7 in) and minimum tread depth (IBC min 11 in).
- Enter the number of flights per floor (2 for a standard switchback stair).
- Read Total Risers and Actual Riser Height (in) to verify equal divisions and IBC compliance.
- Check Comfort Index (2R+T) — the ideal range is 24–25.5 inches for user comfort.
- Use Estimated Weight (lbs) and Stringer Length (ft) for crane picks and precast mold planning.
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