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Construction

Stair Calculator

Design safe, code-compliant stairs with step-by-step calculations and building code compliance checks.

100% FreeBuilding CodesDIY & Professional
Calculator Version
Choose between Basic or Comprehensive calculation modes
Basic Stair Calculator
Quick calculations for standard stair dimensions
Stair Building Basics & Codes

Stringer: The diagonal support framing that holds treads and risers. Its length and angle determine the overall stair geometry.

US Building Codes:
  • • Max step rise: 7.75 inches
  • • Min step rise: 4 inches
  • • Min tread width: 10 inches
  • • Min headroom: 6 feet 8 inches (2032 mm)
  • • Optimal stair angle: 30–50 degrees
How to Use the Calculator
Basic Workflow:
  1. Select "Use One Run" or "Use Total Run"
  2. Enter Run and Total Rise values
  3. Click Calculate → get steps, stringer length, angle
Comprehensive Workflow:
  1. Set step rise (fixed height or step count)
  2. Define tread width, headroom, mount type
  3. Calculate → get detailed dimensions + code compliance
Stair Components & Terminology
Stair Design Visualization

Professional 3D-style stair representation

Upper FloorLower FloorTotal Rise: 120.0"Total Run: 180.0"Stringer Length: 216.3"Stair Angle: 33.7°Step DetailsStep Rise: 6.67"Tread Width: 10.00"Number of Steps: 18Total Rise: 120.0"Total Run: 180.0"
Professional stair design with accurate dimensions
  • Total Rise: Vertical distance from floor to landing
  • Total Run: Horizontal distance from stair start to end
  • Step Rise: Vertical height of one step
  • Tread: Horizontal depth of one step (excluding overhang)
  • Stringer Length: Diagonal length of the support stringer
  • Headroom: Vertical space above stairs for safe passage
Common Stair Design Mistakes
  • Inconsistent step rise: Causes tripping (keep variation < 1/8" between steps)
  • Insufficient headroom: Leads to head injuries
  • Extreme stair angle: Uncomfortable (too steep) or unstable (too shallow)
  • Inadequate tread width: Makes stairs unsafe and uncomfortable