A roofing square equals 100 square feet of roof area. It's the standard unit used by roofers and suppliers. For shingles, 3 bundles typically cover 1 square.

Pitch describes the steepness of a roof as a ratio of rise to run. A "4/12 pitch" means the roof rises 4 inches for every 12 inches of horizontal run. Higher pitch = steeper roof = more surface area.

Waste accounts for cutting, overlaps, starter strips, and mistakes. Simple gable roofs need 10-15% waste. Complex roofs with valleys, dormers, and hips need 15-25%. It's better to have extra than run short.

From inside the attic, hold a level horizontally and measure 12 inches from the rafter. Then measure vertically from the 12" mark to the rafter. That vertical measurement is your pitch (X/12). You can also use smartphone apps that calculate pitch visually.

Gable roofs have two sloped sides meeting at a ridge, with vertical triangular ends. Hip roofs slope on all four sides, meeting at a ridge or point. Hip roofs are more complex and typically have 15-20% more surface area than gables of the same footprint.

Most asphalt shingles come 3 bundles per square (100 sq ft). Divide your total roof area by 100, then multiply by 3. For 1,500 sq ft: 15 squares × 3 = 45 bundles. Add extra for waste and pattern matching.

This calculator handles main roof structures. For complex features, add the waste factor to compensate, or calculate each section separately and add them together. Dormers and valleys significantly increase complexity and waste.

Metal roofing is measured in square feet, not squares. Order panels by total square footage plus waste. Standing seam panels typically come in 12-16" widths and various lengths. Consult your supplier for exact panel counts.

Yes! Google Maps, Google Earth, and specialized roofing software can measure footprints accurately from aerial images. Remember to apply the pitch multiplier — satellite images show flat footprint, not actual sloped area.

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