Divide any irregularly shaped areas of the roof into more manageable triangles and rectangles then calculate square footage for those individual elements and add them to get the total square footage.
Calculating square footage of a pitched roof.
Convert the area to roofing squares.
For example if your roof s pitch is 4 in 12 you would divide 4 by 12.
Because each 100 square feet of roof is one roofing square divide.
Multiply by the square footage of a single floor of your house.
Multiply the length by the width to arrive at.
For example take an area made up of a triangle that s 20 feet high and has a base of 40 feet plus a square that s 40 feet by 40 feet.
A 12 in 12 pitch is a steep 45 degree angle roof.
This would yield 1 3.
How do you calculate square footage for a roof.
So continuing our example if you ve got a two story house with a total square footage of 2 700 square feet with each floor having.
Given pitch and a horizontal area measurement multiply the horizontal area by a correction factor corresponding to pitch provided in the table below to determine the actual area of the roof to be used in the roofing material calculator.
Once you have your roof s pitch divide the number by 12.
A roof s pitch is determined by how much it rises vertically for every foot it runs horizontally.
See the image below for more explanation on rise run and pitch.
Thus a moderate 6 in 12 roof pitch means that the roof rises 6 inches vertically for every 12 horizontal inches it runs.