Roofing Square Feet Calculator

Inches of rise per 12 in of horizontal run. 4:12 is a shallow roof, 12:12 is 45 degrees.
Almost always 12.
Overrides the length derived from the footprint. Use this on any roof that is not a simple gable or hip.
NRCA practice: about 10% on a simple gable, 15% or more on a cut-up hip roof with many valleys.
Squares to buy
24.000
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
2,146.63 ft2
Actual roof surface area
2,400.00 ft2
Roof area including waste
2,400.00 ft2
Roofing squares
24.000
Shingle bundles
72
Underlayment rolls
6
Ridge, hip and valley length
46.33 ft
Hip and ridge cap bundles
3
Eave length (starter strip)
92.66 ft
Drip edge length (full perimeter)
185.33 ft
Common rafter length
25.900 ft
Fasteners needed
7,680
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.
Perimeter figures (eave, drip edge, rafter length) assume a square footprint because only an area was supplied.
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

8 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 2146.63 sq ft x 1.118034 = 2400 sq ft of roof = 24 squares
  6. Bundles = ceil(24 squares x 3) = 72
  7. Underlayment = ceil(2400 / 400) = 6 roll(s)
  8. Ridge + hip + valley = 46.33 ft -> ceil(46.33/20) = 3 cap bundle(s)

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