Roofing material calculator
Roofing in North America is sold by the square: 100 square feet of finished roof.
%
Roofing squares
16.17
- Actual roof area
- 134.16
- Area including waste
- 150.26
- Shingle bundles
- 49
- Underlay rolls At about 27 square metres per roll.
- 6
- Ridge cap pieces
- 50
- Pitch angle
- 26.57 degrees
Show the working
- Plan area of the roof = 120
- Rise per 12 of run = 6
- Waste allowance = 12
- Bundles per square = 3
- Ridge and hip length = 15
- multiplier = hypot(6, 12) / 12 = 1.118 03
- Actual roof area = 120 * 1.118 03 = 134.164
- Area including waste = 134.164 * (1 + 12/100) = 150.264
- sq_ft = 150.264 * 10.763910416709722 = 1617.43
- Roofing squares = 1617.43 / 100 = 16.1743
- Shingle bundles = ceil(16.1743 * 3) = 49
- Underlay rolls = ceil(150.264 / 27) = 6
- Ridge cap pieces = ceil(15 / 0.3) = 50
- Pitch angle = deg(atan(6/12)) = 26.5651
Values are shown to six significant figures here; the arithmetic itself runs on exact fractions and is only rounded where a number is printed.
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The formula
- pitch multiplier = sqrt(rise^2 + 12^2) / 12
- one roofing square = 100 square feet = 9.2903 square metres