The answer is the number of roofing squares for the roof.
How to figure square feet of a roof.
1square of roofing covers 100 square feet of roof a bundle is 1 3 of a square.
Multiply the square footage of your roof by 1 to get the 10 percent waste allowance.
To conclude the example if your total roofing area is 17 300 square feet your waste allowance would be 17 300 x 1 1 730 square feet.
The calculator cannot account for complex shapes based on a measurement of square footage alone.
If your roof measures 48 feet 15 m x 24 feet 7 3 m multiplying its length by its width would give you a square footage of 1 152 square feet 107 0 m 2.
If its pitch is 6 in 12 a pitch multiplier of 1 12 multiplying 1 152 sq ft 107 0 m 2 by 1 12 would give you an overall square footage of 1 290 square feet 120 m 2.
If your roof is flat or has no more than a 3 in 12 pitch you can calculate its total square footage by simply multiplying the length by the width.
The total amount of roofing material you need is 17 300 1 730 19 030 square feet.
Convert the area to roofing squares.
Get the square footage of roof and divide it by 100 and it will give the number of squares you need and for every decimal number over 3 buy a bundle to achieve the amount of material.