Area 
What to Measure 
How to Calculate 


Along Roof 
Overhang (A)Length along roof (B) 
Length of roof (B) x
Overhang Multiplier (see Table B2) 


Dormer 
Distance around dormer (C) 
Number of dormers x distance
around dormer(s) (C) 


Valley 
Number of valleys (D) 
Number of valleys (D) x 6
feet or 1.8 meters 


Downspouts 
Number of downspoutsLength
of downspouts (E) 
Number of downspouts x
length of downspouts (E) x 2 


Table B2
Overhang Multiplier 




Roof Overhang Inches Centimeters 

Multiplier for roof with gutter 
Multiplier for roof without gutter 

Less than 12 
Less than 30 
4.0 
3.0 

12 
30 
4.0 
3.0 

24 
60 
5.3 
4.3 

36 
90 
6.8 
5.8 

48 
120 
8.1 
7.1 

60 
150 
9.6 
8.6 

72 
180 
11.2 
10.2 
