About this calculator
Lay out a straight flight: the number of risers, exact riser height, total run, angle and stringer length, checked against the IRC residential stair rules.
How it’s calculated
Risers = ceil(total rise ÷ maximum riser). Exact riser = total rise ÷ risers. Treads = risers − 1. Run = treads × tread depth. Stringer ≈ √(rise² + (run + one tread)²).
IRC limits: riser 7¾" max, tread 10" min, width 36" min, headroom 6'8".
Worked example
With these inputs:
- Total rise (floor to floor)
- 108 in
- Maximum riser height
- 7.75 in
- Tread depth (going)
- 10 in
- Nosing overhang
- 1 in
- Stair width
- 36 in
the result is:
- Risers
- 14 risers @ 7-11/16"
- Total run (going)
- 10' 10"
- Stair angle
- 37.6°
- Stringer length (approx.)
- 14' 8-13/16"
- Tread board depth (with nosing)
- 11"
Tips from the trade
- Measure the total rise to the finished floor at both ends, not to the subfloor.
- Treat this as a layout check. Local code and the inspector have the final say.
- For stairs wider than 36", add a middle stringer.
Common questions
How many steps for a 9 ft rise?
108" ÷ 7¾" = 13.9, so 14 risers at 7.71".
Results are estimates for planning and pricing. Check quantities against your drawings, the manufacturer’s data and local building codes before ordering.