How to lay out a stair stringer: risers, treads and the code check
A stair starts with one measurement, the total rise. From it the app gives the number of risers, their height, the treads, the total run, the stringer length, the angle and the stairwell opening, and checks them against the code limits.
The limits the app checks
- Riser
- 7-3/4 in at most
- Tread
- 10 in at least
- Headroom
- 6 ft 8 in at least
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Measure the total rise
Measure straight up from the finished floor below to the finished floor above. Count the flooring that will go on top of each level: the stair is laid out to the finished surfaces, not to the subfloor.
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Open Stairs
In Jobsite Calc, tap Tools, then Stairs. The riser limit, the tread depth and the headroom are filled in with the usual code limits. You can change them in Settings.
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Enter the total rise
Type it the way you read it on the tape, for example 9' 1". The app works out the stair as you type.
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Read the risers
The app uses the fewest risers that keep each one under the limit, all the same height. For 9' 1" that is 15 risers of 7-1/4".
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Treads and total run
There is one tread fewer than risers. 14 treads of 10" make a total run of 11' 8". If you have less room, enter the total run you have: the app shortens the treads to fit, and the code check tells you if they get too short.
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Check the code line
Green means every riser is at most 7-3/4", every tread at least 10" and the headroom at least 6' 8". Red names the limit that fails. Local codes differ, so set your own limits in Settings.
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Stairwell opening
The app also gives the length of the floor opening that keeps the headroom, using the floor thickness from Settings. Check it against the framing before you cut.
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Mark and cut the stringer
Set a framing square to the riser height and the tread depth and step it along the stringer, once per riser. The stringer length on screen runs from the first riser to the last, so buy stock longer than that. Drop the bottom of the stringer by one tread thickness, so the first and last steps come out even once the treads are on.
Good to know
All risers are the same
Codes allow only 3/8" between the tallest and the shortest riser in a flight. The app gives one height; keep every riser to it.
The run comes from the treads
Total run is treads times tread depth. A nosing sticks out past each riser but does not change the run.
Pick your fraction
The app rounds to 1/16" by default. Choose 1/8" or 1/32" in Settings, or decimals if you prefer.
The limits are the usual residential ones
A 7-3/4" riser, a 10" tread and 6' 8" of headroom are the limits most US residential codes use. Commercial stairs and other countries differ. Change the limits in Settings and the check follows.
Written for Jobsite Calc 1.0, October 2026.