Your roof is bigger than your house's footprint because of the pitch, and shingles are sold in "squares" (100 sq ft). This calculator accounts for the pitch multiplier and tells you how many bundles to order.
Roof Dimensions
ft
ft
Roof Pitch
Scenario: Your home's footprint is 40 ft x 30 ft with a 6/12 pitch roof.
Result: Footprint area is 1,200 sq ft. The 6/12 pitch multiplier is 1.118, giving 1,342 sq ft of actual roof area. That's 13.4 squares. At 3 bundles per square with 10% waste included, you need 45 bundles.
Most shingles come 3 bundles per square (100 sq ft). Measure your roof footprint, multiply by the pitch factor, divide by 100 to get squares, then multiply by 3 for bundles.
Roof pitch is the rise (vertical inches) per 12 inches of horizontal run. A 6/12 pitch rises 6 inches for every 12 inches across. Steeper pitch means more actual roof area than the footprint suggests, and more shingles needed.
A 2,000 sq ft footprint with a moderate 6/12 pitch has about 2,236 sq ft of roof area, or roughly 23 squares. That's about 69 bundles. Add 15% waste for a total of about 79 bundles.
3-tab asphalt: 15-20 years. Architectural (dimensional) shingles: 25-30 years. Metal roofing: 40-70 years. Poor attic ventilation and sloppy installation will shorten any of those numbers.
Want to learn more before you start your project?
Read the full guide →
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