Rafter Length Calculator
Enter the building span, roof pitch, and overhang to get the rafter length and the standard board length to order for the count you need.
Estimate
How to use the rafter length calculator
- Enter the total building span (width).
- Enter the roof pitch and the overhang in inches.
- Enter how many rafters you need and read the length plus board size.
Questions
How is rafter length calculated?
It is the run (half the span) times the slope multiplier from the pitch, plus the overhang, then rounded up to the next even board length.