Stair
Calculator
Calculate number of steps, rise height, run depth, stringer length, and stair angle. Includes an IRC/IBC building-code compliance check, a live SVG stair diagram, and a lumber estimator.
16
Steps
6.88"
Rise (in)
33.7°
Angle
Find Number of Steps
Enter your total rise and preferred rise/run dimensions. The calculator finds the optimal number of steps.
Number of Steps
16
16 risers / 15 treads
Rise: 6.88" | Run: 11.00"
Rise Each
6.88"
Run Each
11.00"
Stair Diagram
Steps
16 risers
Stringer Len.
16.53 ft
Angle
33.7°
Total Run
13.75 ft
Stair Dimensions — 16 Steps
Risers
16
Treads
15
Rise per Step
6.875"
Tread Depth
11.000"
Total Rise
9.167 ft
Total Run
13.750 ft
Stringer Length
16.525 ft
Stair Angle
33.69°
Rise+Run Sum
17.88"
2×Rise+Run
24.75"
Stair Width
3.00 ft
Headroom
6.67 ft
IRC / IBC Building Code Check
Material Estimate
Stringers
3
pieces (2×12 lumber)
Treads
15
boards needed
Riser Boards
16
boards needed
Railing
16.5
linear feet
Stringer Length
16.53
ft each stringer
Stair Width
3
ft required
Stair Design Fundamentals
Properly designed stairs balance safety, comfort, and building-code minimums all at once. The key relationship is the "rise plus run" rule: your rise per step added to your tread depth should land between 17 and 18 inches for a comfortable climb. Another rule of thumb says twice the rise plus the run should fall between 24 and 25 inches — both are just different lenses on the same steepness trade-off.
🧮 Key Formulas & Building Code (IRC)
Number of risers = round(Total Rise / Preferred Rise) Actual Rise per step = Total Rise / Number of Risers
Total Run = (Number of Risers − 1) × Tread Depth Stringer Length = √(Total Rise² + Total Run²) Stair Angle = arctan(Total Rise / Total Run)
IRC Residential Code Minimums: Max rise per step: 7¾ inches (196mm) · Min tread depth: 10 inches (254mm) · Min stair width: 36 inches (914mm) · Min headroom: 6'8" = 80 inches (2032mm) · Max nosing: 1¼ inches (32mm) · Comfortable range: rise 6.5-7.5 in, tread 10-11 in— FAQ