Calculating The Amount Of Siding Material Required For Your Home  Part 2
Note: Depending on the shape of your home you may have more than 2 gables. As well with complex roof designs you could have a variety of shapes to calculate. Just add the additional roof components to the total.
Gable = 
Half of (DC) X B = Half of C X (AB) = B X C = 

Total For One Gambrel Gable = 
As an example: 
A 
B 
C 
D 
9' 
5' 
20' 
30' 
Gable = 
1/2 ( 3020 ) X 5 = 1/2 X 10 X 5 + 1/2 ( 20 ) X ( 9  5) = 10 X 4 + 5 X 20 Total For One Gambrel Gable 
= 25 + = 40 + = 100 = 165 sq. ft. 
Dormer:
The side of a dormer is a triangle, but as there are two sides, the calculation is actually quite simple.
Figure 4  Measuring a roof dormer for siding
If both sides of the dormer are the same dimensions, the formula is (for both sides  do not multiple times 2):
Length X Width = ____________
If it is necessary to calculate the sides of the dormers individually, the formula for each side of the dormer is:
1/2 X Length X Width = ____________
Once you have calculated all the areas that you wish to have sided, add the numbers together. Then deduct any major nonsided areas, such as garage doors and bay windows. The resultant number is how many square feet of siding you need to cover the areas of the home you wish to be sided.
Starter Strip:
The starter strip is the trim that goes all the way around the perimeter of your home, as shown in Figure 5. It is the trim piece that the first sheet of siding will lock into.
Figure 5  Measuring the perimeter of a home for a siding starter strip
Part 1  Part 3 