Rafter Length Calculator

Rafter is a series of sloped structural members extended from ridge to the wall plate. It is designed to support the roof deck and its related loads. It is the beam supporting the building. So in building with the roof rafters, it is important to know the rafter length to make it seat on the rafter. Use our online Rafter Length Calculator to quickly compute the length of the shed roof rafter by entering the measurement of overhead, roof span, pitch and angle.

Shed Roof Rafter Calculator

Roof Span
Pitch /12
Angle degree
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Rafter Length using Angle = V + R/(2cos(A)) Rafter Length using Pitch = V + (R/2)sqrt(1+P2) Where, V = Overhang R = Roof Span P = Pitch


A roof span of 8 feet has an angle of 35° and an overhead of 12 feet. Calculate its rafter length?


Shed Roof Rafter Length = 12 + 8 / (2cos(35))
= 16.8831 feet

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