Roofing Angles Calculator

Inches of rise per 12 in of horizontal run. 4:12 is a shallow roof, 12:12 is 45 degrees.
Almost always 12.
Squares to buy
14.758
Roofing Calculator
Pitch
6:12
Rise per 12 in of run
6.0000 in
Slope (pitch) factor
1.118034
Roof angle
26.5651 deg
Slope
50.000 %
Hip / valley factor
1.500000
Hip / valley rafter angle
19.4712 deg
Seat (level) cut angle
63.4349 deg
Horizontal footprint area
1,200.00 ft2
Actual roof surface area
1,341.64 ft2
Roof area including waste
1,475.80 ft2
Roofing squares
13.416
Shingle bundles
45
Underlayment rolls
4
Ridge, hip and valley length
40.00 ft
Hip and ridge cap bundles
2
Eave length (starter strip)
80.00 ft
Drip edge length (full perimeter)
140.00 ft
Common rafter length
16.771 ft
Fasteners needed
4,723
Worked out from NRCA Roofing Manual: Steep-slope Roof Systems (roof area from plan area x slope factor; one square = 100 sq ft) and 3 other sources.
Rafter, truss and sheathing sizing, and the ice-barrier, underlayment and fastening requirements for your wind zone, are set by the building code adopted locally and by the shingle manufacturer's installation instructions. Confirm quantities against a physical measure-up before ordering.

How this is worked out

9 steps
  1. Pitch 6:12 -> slope factor = sqrt(6^2 + 12^2) / 12 = 1.118034
  2. Slope angle = atan(6/12) = 26.5651 deg (50% grade)
  3. Hip / valley factor = sqrt(6^2 + 2 x 12^2) / 12 = 1.5
  4. Hip / valley rafter angle = atan(6 / (12 x sqrt(2))) = 19.4712 deg; seat cut = 90 - 26.5651 = 63.4349 deg
  5. Plan area 1200 sq ft x 1.118034 = 1341.64 sq ft of roof = 13.416 squares
  6. Waste 10%: 1475.8 sq ft = 14.758 squares
  7. Bundles = ceil(14.758 squares x 3) = 45
  8. Underlayment = ceil(1475.8 / 400) = 4 roll(s)
  9. Ridge + hip + valley = 40 ft -> ceil(40/20) = 2 cap bundle(s)

Results are general information, not financial, tax, legal, medical or engineering advice.