Stair Stringer Calculator
Calculate stair riser count, actual riser height, total run, stringer length, angle, stringer quantity and stock-material cost.
Default project preview
13.93 ft
Actual riser height
7.5 in
Total horizontal run
10.83 ft
Stair angle
38.9°
Stringer quantity
5
Calculator
Build the material order
Your order will appear here
Enter the project details and calculate a rounded material estimate.
Input and output guide
What each value means
The labels and units below are part of this calculator’s visible methodology. Replace every default with measurements or product data from the actual project.
Total stair rise
Enter this project assumption in in. The current imperial default is 105 in.
Target maximum riser
Enter this project assumption in in. The current imperial default is 7.5 in.
Tread depth
Enter this project assumption in in. The current imperial default is 10 in.
Stair width
Enter this project assumption in ft. The current imperial default is 4 ft.
Maximum stringer spacing
Enter this project assumption in in. The current imperial default is 16 in.
Available stock length
Enter this project assumption in ft. The current imperial default is 16 ft.
Extra stock allowance
Enter this project assumption in %. The current imperial default is 10 %. Minimum: 0. Maximum: 50.
Price per stock piece
Enter this project assumption in a unitless value. The current imperial default is 32. Minimum: 0.
How to read the outputs
Actual riser height
14 equal risers. Default preview: 7.5 in.
Total horizontal run
13 tread spaces. Default preview: 10.83 ft.
Stair angle
rise-to-run geometry. Default preview: 38.9°.
Stringer quantity
maximum entered spacing. Default preview: 5.
Stock pieces
1 per stringer before allowance. Default preview: 6.
Stock cost
full stock pieces. Default preview: $192.00.
Methodology
Transparent calculation
BuildMeter converts every input to a consistent internal unit, applies the selected allowance, and rounds products up to whole purchasable units.
Risers = round up (total rise ÷ target riser). Actual riser = total rise ÷ risers. Run = tread depth × (risers − 1). Stringer length is the hypotenuse.
Reviewed project guidance
How to use this estimate in a real project
Last reviewed: July 29, 2026
This calculator lays out stair rise, run, tread count and stringer length from total rise and target geometry. It is a planning check, not approval of stair dimensions, headroom, landings or stringer capacity.
Calculation steps
- 1Measure finished-floor to finished-floor rise.
- 2Choose a whole riser count that produces an acceptable actual rise.
- 3Use one fewer tread than risers for a typical upper-floor termination.
- 4Calculate total run and diagonal stringer length.
Worked numerical example
A total rise of 105 in divided into 15 risers gives 7 in per riser. With 14 treads at 10 in run, the horizontal run is 140 in and the diagonal stringer line is about 175 in.
Purchasing and rounding
Stringer stock must be long enough for the diagonal line plus end cuts. Lumber grade, depth remaining at notches and support conditions control whether a cut stringer is suitable.
Interpret the result
Small changes in riser count change every riser. The final field layout should be checked from finished surfaces, not rough framing alone.
Page-specific assumptions
- Straight stair flight.
- Uniform risers and treads.
- No winders or curved geometry.
- Finished surface thicknesses are accounted for.
Common mistakes
- Measuring rough-to-rough instead of finish-to-finish.
- Using equal numbers of risers and treads without checking termination.
- Forgetting floor and tread finishes.
- Choosing lumber only by calculated length.
Primary and technical references
BuildMeter provides planning estimates, not engineering, architectural, electrical, mechanical, plumbing, permit or code approval. Review the methodology and verify final decisions with product documentation and qualified professionals.
FAQ
Stair Stringer Calculator questions
Why is the actual riser different from the target?+
The target sets the maximum planning height. The total rise is divided into an integer number of equal risers.
Why are there usually fewer treads than risers?+
The upper floor or landing commonly serves as the final tread, leaving one fewer horizontal tread space.
Can long stringers be spliced?+
Only with an approved structural detail. Do not assume ordinary field splices are acceptable.