A roofing square equals 100 square feet of roof surface. To order the right amount of shingles, you need to account for the actual pitched surface area — not just the ground footprint.
The Pitch Multiplier
A 6:12 pitch roof has a slope multiplier of 1.118, meaning the actual surface is 11.8% larger than the footprint. This calculator applies the correct pitch multiplier automatically so your bundle count is accurate.
Why Add a Waste Factor?
Straight gable roofs: 10% waste is standard
Complex roofs with hips, valleys, and dormers: 15–20% waste
Never order exactly what you calculate — overage protects against damaged shingles and dye-lot variations
Bundles Per Square
Standard 3-tab shingles: 3 bundles per square
Architectural shingles: typically 3 bundles per square
Some heavy premium products: 4 bundles per square (check manufacturer specs)
What About Underlayment and Ridge Cap?
Felt underlayment: 1 roll covers 4 squares
Synthetic underlayment: 1 roll covers 10–20 squares
Ridge cap shingles: measure linear feet of ridgeline separately
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