Roofing shingle estimator

Enter the building footprint and pick the pitch factor closest to your roof. The estimator adjusts the flat footprint for slope, adds your waste allowance, and converts the result into bundles, squares, and underlayment rolls.

Estimator

Building length (m)

Building width (m)

Roof pitch factor

Waste and cuts allowance (percent)

Formula: roof area = length x width x pitch factor. Area with waste = roof area x (1 + waste / 100). Bundle coverage stated: one bundle covers about 3.1 sq m (about 33.3 sq ft), and 3 bundles make one square. One square equals 100 sq ft, which is 9.2903 sq m. Underlayment guidance stated: one roll covers about 37.16 sq m (400 sq ft). Eaves overhang is not included; add it to length and width if your roof extends past the walls.

Worked example: Building 10 m by 8 m, pitch factor 1.20, waste 10 percent. Footprint = 80 sq m. Roof area = 80 x 1.20 = 96.00 sq m. With waste = 105.60 sq m. Bundles = 105.60 / 3.1 = 34.06, rounded up to 35 bundles. Squares = 105.60 / 9.2903 = 11.37 squares. Underlayment rolls = 105.60 / 37.16 = 2.84, rounded up to 3 rolls.

Estimates only. Roofing involves height, structure, ventilation, and code requirements. This is not a roofing design. Verify measurements and materials with a qualified roofer before ordering or climbing.

Frequently asked questions

What is a roofing square?

A square is 100 square feet of roof area, about 9.29 sq m. Shingles are commonly priced and bundled by the square, with about 3 bundles per square for standard architectural shingles.

Should I add eaves and overhangs?

Yes. This estimator starts from the building footprint. If your roof extends past the walls, increase the length and width you enter so the overhang is included in the area.

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Roofing trade pack

The roofing pack bundles this calculator with a pre-job checklist, a printable material list and a metric and imperial toggle.