Stair Calculator
Calculate stair dimensions, riser and tread counts, stringer length, stair angle, and material estimates. Includes IRC building code compliance checks for residential stairs.
Comfort / Best Practice Warnings
- Rise + Run = 18.21". The ideal range is 17" to 18" for comfortable stairs.
Stair Dimensions
Number of Risers
14
steps up
Actual Riser Height
7.71"
per step
Number of Treads
13
treads needed
Total Run
11.4 ft
136.5" horizontal
Stringer Length
14.5 ft
174.1"
Stair Angle
38.4°
from horizontal
Stairwell Opening
12.4 ft
148.5" min length
Rise + Run
18.21"
ideal: 17"–18"
Material Estimates
Tread Boards
13
39.0 linear ft of tread stock
Riser Boards
14
42.0 linear ft of riser stock
Stringers (2x12)
3
each 14.5 ft long
Stringer Board Feet
5.1
board feet total
How to Use This Calculator
Enter the total rise (the vertical height the stairs must climb) in feet and inches. Adjust the target riser height (7.5 inches is standard) and run depth (10-11 inches is typical). The calculator will determine the number of risers and treads, actual riser height, total run, stringer length, and stair angle. It also checks whether your dimensions meet IRC residential building code requirements.
Formula Used
Number of Risers = Total Rise / Target Riser Height (rounded). Actual Riser Height = Total Rise / Number of Risers. Total Run = Number of Treads x Run Depth. Stringer Length = sqrt(Total Rise squared + Total Run squared). Stair Angle = arctan(Total Rise / Total Run).
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Disclaimer
This calculator is for estimation purposes only. Always verify measurements on-site and consult local building codes, which may differ from IRC standards. A licensed professional should review stair designs before construction.