Roof Pitch

Definition

Roof pitch is rise per 12 inches of run: 6/12 is arctan(6/12) ≈ 26.6°. Run of a common rafter is half the span minus half the ridge. Rise follows the pitch ratio; the hypotenuse is birdsmouth-to-ridge length. The unit toggle converts span and overhang but leaves the 6/12 ratio alone — it does not become 6/300 in millimetres.

Calculators that use this

• Carpentry & framing

  Roof Pitch & Rafter Length Calculator

  Calculate common rafter length, pitch angle, rise and overhang from building span and a rise-per-12 pitch.

• Carpentry & framing

  Stair Rise and Run Calculator

  Size stair risers, treads and stringer length from total rise and a target step height. Works in inches or millimetres.