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Stair Stringer Calculator
Give it the total rise from finished floor to finished floor. This divides it into legal risers, sets the tread depth, and returns the stringer length and how far the stairs will project into the room.
Your numbers
Result
Number of risers
14
risers
- Each riser
- 7.714in
- Treads
- 13treads
- Total runHow far it projects
- 136.5in
- Stringer length
- 14.5ft
- Buy stringer stock
- 16ft
- Stair angle
- 38.4°
- Opening height neededRise + 80 in headroom
- 188in
How this is calculated
- Risers = total rise ÷ target riser, rounded to a whole number. You cannot have a fractional step.
- Each riser = total rise ÷ number of risers. This is why the answer is rarely a round number.
- Treads = risers − 1, because the top step is the floor itself.
- Stringer length = √(total rise² + total run²).
Before you order
- Every riser must be within 3/8 in of every other one. Uneven risers are the leading cause of stair falls and the thing an inspector measures first.
- Typical residential code allows a maximum 7.75 in riser and requires a minimum 10 in tread. Check your local amendments.
- Cutting stringers removes material — allow for the thickness of the tread at the top and bottom when you lay out the birdsmouth.
- Minimum headroom is usually 6 ft 8 in measured vertically from the tread nosing line.
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