How it’s calculated
A sloped roof is larger than its footprint. For a pitch of rise inches per 12 in of run, each horizontal square foot becomes √(1 + (rise/12)²) square feet of roof. This works for simple gable and hip roofs that share one pitch.
Example: a 40 × 30 ft footprint (1,200 ft²) with a 6/12 pitch: multiplier √1.25 = 1.118, roof area 1,341.6 ft² = 13.42 squares. With 10% waste: 14.76 squares × 3 = 44.3 → 45 bundles.
Frequently asked questions
How many bundles of shingles are in a square?
Three for most 3-tab and architectural asphalt shingles, each bundle covering about 33⅓ ft². A roofing square is 100 ft².
How do I calculate roof area from the ground?
Measure the house footprint including the eave and rake overhangs, then multiply by the pitch factor: 1.054 for 4/12, 1.118 for 6/12, 1.202 for 8/12, 1.302 for 10/12 and 1.414 for 12/12.
How many squares is a 2,000 square foot house roof?
It depends on pitch and overhang. A 2,000 ft² single-story footprint at 6/12 is about 2,236 ft² of roof, or 22.4 squares before waste.
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Sources
- How Many Bundles of Shingles Are in a Square? — GAF
- Right triangles and the Pythagorean theorem (Algebra and Trigonometry 2e) — OpenStax
Formulas are taken from the free public references above. Results are provided “as is” for informational and educational purposes only. See our disclaimer.
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