Stair Stringer Length
Diagonal stringer length and 2x12 board feet from rise and run.
Example
You enter
- Total rise (in) 108
- Total run (in) 144
- Tread cut depth (in) 1
You get
- Stringer length 180 in
- Stringer feet 15 ft
- Board feet (2x12 stringer) 21.09
Details, formula, and sources
Stringer length = sqrt((rise × n_risers)² + (run × n_treads)²) plus rise / drop adjustments at top and bottom plates.
IRC 2021 (International Residential Code). §R311.7.
Free read-only access at codes.iccsafe.org.
Estimate. AHJ and licensed structural engineer govern.
Field names used by the API: total_rise_in, total_run_in, tread_cut_depth_in, stringer_in, stringer_ft, board_feet