Turn a total rise into a code-compliant set of stairs: number of steps, exact riser height, total run and stringer length. Based on the IRC 7¾ in riser limit.
| Input | Result |
|---|---|
| 108 in total rise, 10 in tread | 14 steps · 7.71 in riser · 140 in run · 176.82 in stringer |
| 96 in total rise, 10 in tread | 13 steps · 7.38 in riser · 130 in run · 161.6 in stringer |
| 60 in total rise, 11 in tread | 8 steps · 7.5 in riser · 88 in run · 106.51 in stringer |
Under the 2018 International Residential Code (IRC R311.7.5), a residential stair is constrained by two dimensions: the riser may not exceed 7¾ in (196 mm), measured vertically between the leading edges of adjacent treads, and the tread may not be less than 10 in (254 mm), measured horizontally between those same leading edges. Within any single flight, the tallest riser may not exceed the shortest by more than ⅜ in, and the same ⅜ in tolerance applies across tread depths, that consistency matters more than the individual numbers, because an uneven step is what trips people.
The calculator works backwards from the first limit: it divides your total rise by 7¾ in, rounds up to a whole number of steps, then shares the rise equally. Rounding up is what keeps every riser legal, rounding down would push one step over the cap. Headroom is a separate rule (IRC R311.7.2 sets a minimum of 6 ft 8 in) and is not something a length-and-height calculation can check for you.
Local amendments exist and commercial stairs fall under the IBC instead, so treat the output as a layout starting point and confirm the finished stair with your building department.
Under the 2018 IRC (R311.7.5.1) the riser may not exceed 7¾ in (196 mm), measured vertically between the leading edges of adjacent treads. The tallest riser in a flight may not exceed the shortest by more than ⅜ in.
IRC R311.7.5.2 sets a minimum of 10 in (254 mm), measured horizontally between the leading edges of adjacent treads, with the same ⅜ in consistency tolerance across the flight.
Because rounding down would make at least one riser taller than the 7¾ in cap. Rounding up guarantees every riser is at or under the limit.
No. IRC R311.7.2 requires at least 6 ft 8 in of headroom measured vertically from the sloped plane of the tread nosings, which depends on your floor opening and framing, not on the rise and run alone.
Most US residential work is, but jurisdictions amend it and commercial stairs fall under the IBC. Confirm the finished stair with your local building department.