Roof Rafter Length
Construction & DIYCalculate roof rafter length, line length, rise, and overhang dimensions from roof span, run, and pitch (in/ft or degrees) for framing gable and shed roofs.
Pitch 6/12 (26.6°) · rafter to wall 15.65 ft
About this calculator
Roof framing requires precise mathematical calculation of rafter lengths, bird's mouth seat cuts, and overhang tails to ensure a stable, weather-resistant roof structure.
This tool computes the theoretical rafter line length, vertical rise, ridge deduction, and actual cut length with eave overhang from roof pitch (e.g. 4/12, 6/12, 8/12) and building span.
How It Works & Formula
Run = Span / 2 (for gable roofs). Rise = Run × (Pitch / 12). Rafter Line Length = √(Run² + Rise²). Total Rafter Length = Line Length + Overhang Length - Half Ridge Thickness.
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