Free Calculator
Rafter Length Calculator
Calculate rafter length, span, and recommended size for roof framing. Enter building dimensions.
Enter Building & Roof Details
Building Width (span from center to center)
ft
Roof Pitch
in 12
4:12 - 18.43°
5:12 - 22.62°
6:12 - 26.57°
7:12 - 30.26°
8:12 - 33.69°
9:12 - 36.87°
10:12 - 39.81°
12:12 - 45°
Rafter Spacing
12 inches (common)
16 inches (standard)
19.2 inches (TJI spacing)
24 inches (maximum)
Wood Species
Douglas Fir-Larch
Hem-Fir
Southern Pine
Douglas Fir (North)
Southern Pine (North)
Calculate Rafter Length
Rafter Calculations
Rafter Length
-
feet
Total Span
-
feet
Rise
-
inches
Slope Length
-
inches per ft
Board Feet
-
per rafter
Recommended Size
-
minimum
Rafter Size Chart (Based on IRC)
Span
12" o.c.
16" o.c.
24" o.c.
Rafter Anatomy
SPAN
RISE
RAFTER
Plate
Ridge