Stair calculator for construction
Easily determine stair dimensions including rise, run, number of steps, stringer length, total materials, and code compliance. Includes a live diagram and educational tips for building safe, code-conforming stairs.
Input parameters
Calculated results
Results will appear here after calculation.
Stair diagram
Building code compliance checks
- Max riser height per most codes: typically ≤ 180 mm
- Min tread run per most codes: typically ≥ 250 mm
- Consistent rise & run (variation ≤ 6 mm)
Educational notes
- Riser: The vertical height difference between treads. Residential codes usually limit each riser to 175–180 mm (7 in). Consistency is important for safety.
- Run (Going): The horizontal depth of a step (tread minus nosing overhang). Code minimum is often 250 mm (10 in).
- Stair width: Most codes require stairs to be at least 900 mm (36 in) wide.
- Stringer: The diagonal board that supports the treads and risers. Open stringers are cut to profile; closed stringers are routed or notched.
- Stringers are best constructed of strong lumber (e.g., 2x12, 38x286 mm). Support is critical for long or wide stairs.
- Always check your local building codes for specifics. The above values are international minimums; your region may differ.
Safety tips:
- Ensure solid handrails and slip-resistant treads.
- Uniform rise/run and adequate lighting prevent falls.
- For long stairs, consider intermediate landings/easy runs.