Stair Calculator
Calculate stair geometry with IRC building code compliance checking. Get precise stringer dimensions and printable cutting templates.
⚠️ Professional Verification Required
This calculator provides estimates based on IRC building codes. Always consult with a licensed contractor or building inspector before construction. Building codes vary by jurisdiction.
Stair Dimensions
Calculation Results
Stringer Cut Guide
Recommended Material: Use 2×12 lumber for stringers. Ensure at least 5" of material remains after cutting notches for structural integrity.
Number of Stringers Needed
Install one stringer on each side, plus one or more in the center. For wider stairs (>36"), add additional center stringers every 16".
Notch Dimensions (per step)
Top & Bottom Cuts
Remove tread thickness from first riser height to account for tread material
Cutting Instructions
- 1.Mark the rise and run dimensions on your framing square.
- 2.Align the square on the 2×12 and mark each notch (14 treads total).
- 3.Cut notches with a circular saw, finishing corners with a handsaw.
- 4.Verify minimum 5" of material remains after notching.
- 5.Use the first stringer as a template for remaining stringers.
IRC Building Codes
Rise Requirements
IRC requires riser height between 7" and 7.75". The maximum difference between any two risers cannot exceed 3/8".
Tread Requirements
Minimum tread depth is 10" measured horizontally. Nosing can project 0.75" to 1.25" beyond the tread below.
Headroom
Minimum 6'8" (80") vertical clearance above the nosing line is required throughout the stairway.
Stringer Sizing
Use 2×12 lumber for stringers. Ensure minimum 5" remains after notching for adequate structural support.