Stair Calculator
Calculate stair riser count, actual rise, total run, stringer length, tread boards, fasteners and material cost.
Default project preview
13 risers
Actual riser height
7.38 in
Treads
12
Required run
126 in
Stringers
4
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 vertical rise
Enter this project assumption in in. The current imperial default is 96 in.
Available horizontal run
Enter this project assumption in in. The current imperial default is 132 in.
Target maximum riser
Enter this project assumption in in. The current imperial default is 7.5 in.
Planned tread depth
Enter this project assumption in in. The current imperial default is 10.5 in.
Stair width
Enter this project assumption in in. The current imperial default is 36 in.
Maximum stringer spacing
Enter this project assumption in in. The current imperial default is 16 in.
Stock stringer length
Enter this project assumption in ft. The current imperial default is 16 ft.
Tread board face width
Enter this project assumption in in. The current imperial default is 5.5 in.
Tread stock-board length
Enter this project assumption in ft. The current imperial default is 12 ft.
Price per stringer board
Enter this project assumption in a unitless value. The current imperial default is 35. Minimum: 0.
Price per tread board
Enter this project assumption in a unitless value. The current imperial default is 18. Minimum: 0.
Price per 100 fasteners
Enter this project assumption in a unitless value. The current imperial default is 10. Minimum: 0.
How to read the outputs
Actual riser height
equal risers. Default preview: 7.38 in.
Treads
10.5 in planned depth. Default preview: 12.
Required run
available 132. Default preview: 126 in.
Stringers
16 in maximum spacing. Default preview: 4.
Stringer length
fits entered stock length. Default preview: 13.2 ft.
Tread boards
2 boards across each tread. Default preview: 6.
Fasteners
2 packs of 100. Default preview: 192.
Material cost
stringers, treads and fasteners. Default preview: $268.00.
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 rise = total rise ÷ risers. Treads = risers − 1. Required run = treads × tread depth. Stringer length = √(rise² + run²).
Reviewed project guidance
How to use this estimate in a real project
Last reviewed: July 29, 2026
Use this calculator to lay out a straight stair from total rise, target riser height and available run. It provides geometry for planning, not approval of tread, headroom, width, landing or guard requirements.
Calculation steps
- 1Measure finished-floor-to-finished-floor rise.
- 2Choose a whole riser count near the target height.
- 3Divide total rise exactly by riser count.
- 4Multiply tread count by selected run and verify the complete stair envelope.
Worked numerical example
A total rise of 108 in divided into 15 risers gives 7.2 in per riser. Fourteen treads at 10.5 in each require 147 in of horizontal run.
Purchasing and rounding
Stringer, tread, riser, landing and railing quantities depend on the approved geometry and framing system. Do not cut materials before field verification.
Interpret the result
Changing riser count changes both riser height and stair length. Uniformity is as important as the average dimension.
Page-specific assumptions
- Straight flight.
- Finished elevations are known.
- Uniform risers and treads.
- No winders or curved sections.
Common mistakes
- Measuring rough instead of finished elevations.
- Using one target riser without recalculating exact uniform height.
- Forgetting tread count is usually one less than riser count.
- Ignoring headroom and landings.
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 Calculator questions
Why must every riser be equal?+
Unequal risers create a serious trip hazard and are restricted by building codes. Final construction measurements must be precise.
Does this approve a stair for code compliance?+
No. It is a planning calculator. Local rules govern geometry, landings, guards, handrails, headroom and structure.
Why can required run exceed available run?+
The chosen tread depth multiplied by the number of treads may need more horizontal space than entered. The design must then change.