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) 30
Checked against published worked examples from: Naval Education and Training Professional Development and Technology Center (US Navy).
Details, formula, and sources
Formula or tableStringer length = sqrt(total_rise² + total_run²); board feet on a nominal 2x12.
Source and editionIRC 2024 (International Residential Code). §R318.7 [R311.7 in IRC 2021].
Free accessFree read-only access at codes.iccsafe.org.
What governsEstimate. AHJ and licensed structural engineer govern.
API field namestotal_rise_in, total_run_in, tread_cut_depth_in, stringer_in, stringer_ft, board_feet