Roofing Squares and Bundles
Squares, bundles per shingle product, underlayment rolls, drip edge.
Example
You enter
- Roof area, SLOPED surface (ft²; a plan footprint x the pitch factor) 2200
- Pitch rise (in / 12) 6
- Shingle product architectural
- Perimeter (ft) 200
You get
- Squares 24.6
- Bundles 74
- Underlayment rolls 7
- Drip edge / starter (lf) 200
- Starter strip (LF) 200
- Waste factor 0.12
No published worked example is on file for this calculation. It is checked against a hand-worked derivation of its method and an independent reference test.
Details, formula, and sources
Formula or tableSquares = roof_area / 100 ft² + pitch-based waste factor; bundles = squares × bundles_per_square (typically 3 for 3-tab, 3-4 for architectural). Underlayment + drip edge from linear quantities.
Source and editionARMA (Asphalt Roofing Manufacturers Association) Residential Asphalt Roofing Manual by name. IRC 2024 (International Residential Code). §R905 (unchanged from 2021).
Free accessARMA manuals free at asphaltroofing.org. Free read-only access at codes.iccsafe.org.
What governsEstimate. AHJ and licensed professional govern.
API field namesroof_area_ft2, pitch_rise, shingle_product, perimeter_ft, squares, bundles, underlayment_rolls, drip_edge_lf, starter_strip_lf, waste_factor
- Pitch-based waste factor 10% (below 6/12) / 12% (6-8/12) / 15% (9-11/12) / 18% (12/12 and steeper), on the SLOPED roof area; shingle makers set waste by roof size and gable vs hip, so treat these as defaultsengineering practice