Rafter Calculator

Calculate rafter dimensions and cutting angles for your roof

Roof Specifications

Building Span (feet)

Roof Pitch (rise per 12")

Overhang (inches)

Rafter Spacing (inches)

Rafter Dimensions

Run (Horizontal)

12.00 feet

Rise (Vertical)

72.00 inches

Rafter Length

13.42 feet

Without overhang

Total Rafter Length

14.42 feet

With overhang

Roof Angle

26.57°

Birdsmouth Depth

3.50 inches

Rafters needed (40' building): 31

Total board feet (2×6): 447