Stair Stringer Layout (with code check)
Riser count, exact rise, total run, stringer hypotenuse, throat depth.
Example
You enter
- Total rise (in) 108
- Target rise (in) 6.75
You get
- Riser count 16
- Exact rise 6.75 in
- Tread depth 11 in
- Tread count 15
- Total run 165
- Angle (deg) 33.21
- Rise pass Yes
- Tread pass Yes
Details, formula, and sources
Riser count, exact rise, total run, stringer hypotenuse, throat depth, and pass/fail against your AHJ's max rise / min tread.
Riser count = ceil(total_rise / target_rise). Exact rise = total / count. Total run = (count − 1) × tread. Stringer hypotenuse = sqrt(rise² + run²). Throat depth = stringer_thickness × cos(theta) − exact_rise × sin(theta) where theta = atan2(rise, run). Pass/fail against user-entered local-code rise max and tread min.
IRC 2021 (International Residential Code). §R311.7 referenced by name; the user supplies the AHJ's adopted max rise and min tread (the tile does not bundle code values).
Free read-only access at codes.iccsafe.org.
Estimate. AHJ and licensed structural engineer govern.
Field names used by the API: total_rise_in, target_rise_in, riser_count, exact_rise_in, tread_depth_in, tread_count, total_run_in, angle_deg, rise_pass, tread_pass
- Default target rise / tread 7.0 in / 11.0 in (engineering practice typical)engineering practice
- Default code max rise / min tread 7.75 in / 10.0 in (IRC 2021 §R311.7 typical; verify your AHJ)IRC 2021 default