Rafter Length Calculator
Estimate common rafter length from run and pitch.
Use this rafter length calculator to estimate common rafter length from the roof run and pitch. Multiply the run by the pitch factor: √(1 + (rise/12)²). For example, a 6:12 roof has a pitch factor of 1.118. Add the required overhang to the calculated rafter length.
Rafter length
16.65
ft (incl. 12 in overhang)
Pitch factor
1.118
6:12
Roof angle
26.6
degrees
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How does the rafter length calculator work?
Rafter length = run × pitch factor, where the pitch factor is √(1 + (rise/12)²). A 6:12 roof has a factor of 1.118, a 12:12 roof is 1.414.
What else do people ask about this calculator?
How long is a rafter for a 24 ft wide house at 6:12?
Run = 12 ft. Rafter = 12 × 1.118 = 13.4 ft, plus overhang.
How do I convert pitch to degrees?
angle = arctan(rise / 12). 4:12 = 18.4°, 6:12 = 26.6°, 8:12 = 33.7°, 12:12 = 45°.
Which related calculators should I use next?
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