Roof Rafter Length
Rafter² = run² + rise². Pythagorean from pitch + run.
Result
Rafter length
13.42 ft
Rise 6.00 ft · angle 26.6°.
- Pitch6/12
- Run12 ft
- Rise6.000 ft
- Rafter13.416 ft
- Angle26.565°
Step-by-step
- Rise = pitch × run / 12 = 6 × 12 / 12 = 6.000 ft.
- Rafter = √(run² + rise²) = √(144 + 36.000) = 13.416 ft.
How to use this calculator
- Enter pitch (X/12) + horizontal run.
About this calculator
Roof pitch is rise per 12 inches of run. 6/12 pitch = 6" rise per 12" run = ~26.6° angle. Rafter length = hypotenuse of right triangle: √(run² + rise²). Add foot for overhang + tail cut. Common pitches: 4/12 (low slope), 6/12 (standard), 12/12 (steep). Higher pitch sheds water/snow better; eats more material. Source: International Residential Code (IRC) §R802.
Frequently asked
Each unit of run goes up 12 units. 12/12 = 45° = "12 pitch."
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