Rafter Line Length Calculator
Deduct half the thickness of the ridge
from the span length
this length
is the correct measurement from the top plumb line to the birdsmouth plumb line.
To get overall plumb to plumb length
add
overhang horizontal length
to
horizontal span
(less subfascia and fascia thickness)
Horizontal Span of Rafter(inches,run)
Roof Pitch (inches rise per foot of run)
1
1.5
2
2.5
3
3.5
4
4.5
5
5.5
6
6.5
7
7.5
8
8.5
9
9.5
10
10.5
11
11.5
12
14
16
18
24
Plumb to plumb line length (inches) =