Roofing calculator

32.8 sq ft per Duration bundle. 98.4 ÷ 3.

Cuts, hips, and starter leftovers. 10% is a planning start, not a code. A simple gable can be less. A cut-up roof can be more.

Job sheet

Plumb roofing job sheet

6 in 12 pitch.

  • Roof surface1,230 sq ftPlan area times pitch factor. Net surface before waste was 1,118 sq ft.
  • Squares12.31 square = 100 sq ft of roof surface.
  • Bundles3832.8 sq ft per bundle. Duration is 32.8.
Plumb roofing job sheet
6 in 12 pitch.

Roof surface: 1,230 sq ft (Plan area times pitch factor. Net surface before waste was 1,118 sq ft.)
Squares: 12.3 (1 square = 100 sq ft of roof surface.)
Bundles: 38 (32.8 sq ft per bundle. Duration is 32.8.)

Pitch factor

The factor is the slope length of a 12 inch run: square root of (12² + rise²), divided by 12. A 6/12 is about 1.118. Multiply the plan area, the footprint, by that factor. Then divide by 100 for squares.

Duration’s published coverage is 98.4 square feet for three bundles. That is 32.8 square feet a bundle, not a flat 33.3. A 1,000 square foot plan at 6/12 is about 1,118 square feet of roof. At 10% extra that is about 1,230 square feet, 12.3 squares, and 38 bundles of Duration before you round the last one. Hip and ridge caps are a separate product. They are not inside the 98.4.

Metal roofing uses the same squares. Type the square feet one panel covers, from that panel’s sheet, into the bundle box. Rafter length is the rafter calculator. Sheathing sheets are plywood. The flat area, before pitch, can come from the square foot calculator.

FAQ

What is a roofing square?

100 square feet of roof surface, not of the floor under it. A 1,000 square foot plan at a 6/12 pitch is more than 10 squares because the roof is longer than the ceiling.

How many bundles of shingles?

Owens Corning TruDefinition Duration publishes 98.4 square feet per square and 3 bundles, so one bundle is 32.8 square feet. Divide the roof surface by 32.8 and round up. A different shingle prints a different coverage. Type that number.

Sources

  1. Owens Corning TruDefinition Duration: 64 shingles per square, 3 bundles per square, 98.4 sq ft coverage per square.
  2. Owens Corning Duration data sheet: Same coverage figures: 3 bundles, 98.4 sq ft per square.