Be sure to add estimated measurements into each side's total to account for the overhangs. Mark these measurements on your diagram.
 Add up the square feet you determined for each section. The sum of these numbers if your total square feet of the house, not the roof.
 To calculate the square of a roof, take the number of square feet and divide it by 100.
 The pitch is how steep the roof is. Pitch is calculated by the roof's rise over its run. Measure from the edge of the roof over 12 inches (12 is the run) and see how many inches up the roof line is (this is the rise). Get a slope multiplier from the chart below. Roof Pitch Slope Multiplier Chart: 2 in 12 = 1.102, 3 in 12 = 1.134, 4 in 12 = 1.159, 5 in 12 = 1.191, 6 in 12 = 1.230, 7 in 12 = 1.274, 8 in 12 = 1.322, 9 in 12 = 1.375, 10 in 12 = 1.432, 11 in 12 = 1.493, 12 in 12 = 1.554.
 Take the ground level square figure you came up with and multiply it by the appropriate slope multiplier. This will give you your roof square.
Measure the four sides of the house from the ground using a measuring tape.
Get the total square feet.
Calculate the number of squares the house is.
Determine the pitch of the roof.
Get the final roof calculation.
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