rafter calculator with birds mouth

Calculate Rafter Length

About Rafter Length Calculator

This calculator determines rafter length, angles, and material requirements for roof construction based on building dimensions and roof pitch.

Rafter Length Formula:

Length = √(Run² + Rise²) + Overhang

Common Rafter Sizes:

  • 2x6: Up to 10 ft span
  • 2x8: Up to 13 ft span
  • 2x10: Up to 16 ft span
  • 2x12: Up to 20 ft span
  • 2x14: Up to 24 ft span

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