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🪜 Stair Calculator & Planner

Calculate stair dimensions, rise, run, and materials for building staircases

Total Rise (Floor to Floor)

Vertical distance from bottom floor to top floor (e.g., 9 feet = 108 inches)

Preferred Dimensions (Optional)

Code: 6-8 inches (7-7.5" ideal)

Code: 9-11 inches (10-11" comfortable)

Minimum 36" for residential (32" for tight spaces with approval)

How to Use

  1. Measure the total vertical rise from finished floor to finished floor
  2. Enter your preferred rise and run (or use defaults)
  3. Enter the desired stair width
  4. Click "Calculate Stair Dimensions" to see results
  5. Verify dimensions meet building codes
  6. Use the stringer length to order lumber

Stair Building Guide

Building Code Requirements

IRC: Rise 7-3/4" max, run 10" minimum. Variation between steps must be ≤ 3/8". Headroom 6'8" minimum. Width 36" minimum for residential.

Comfort Formula

Ideal stairs follow: (2 × Rise) + Run = 24-25 inches. This ensures comfortable climbing. Example: 7.5" rise + 10" run = 25" (perfect).

Stringer Construction

Use 2×12 lumber for stringers. Minimum 3 stringers for 36" wide stairs. Add 4th stringer if over 36". Mark and cut precisely - consistency is critical.

Materials

Treads: 2× lumber or stair treads. Risers: 1× lumber or plywood (if enclosed). Handrails required if 4+ risers. Balusters every 4" maximum spacing.