ft
Length of one roof plane (ridge to eave)
Enter roof length (ft)
ft
Width of one roof plane (gable to gable)
Enter roof width (ft)
planes
Simple gable = 2, hip roof = 4
Enter 1–20 planes
Result
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How Roofing Squares Are Calculated
A roofing square is the standard unit used by roofing contractors — it equals exactly 100 square feet of roof surface. All roofing materials (shingles, felt, ice-and-water shield, ridge cap) are priced and sold by the square or bundle.
The key step most DIYers miss is the pitch factor. Your roof footprint (length x width) is always smaller than the actual roof surface because the slope adds area. A 6:12 pitch has 12% more surface than its footprint; a 12:12 (45°) pitch has 41% more.
Formula
Squares = (Length × Width × Planes × Pitch Factor × Waste Factor) ÷ 100
Example: 60ft × 30ft × 2 planes × 1.12 pitch × 1.10 waste = 4,435 sq ft ÷ 100 = 44.4 squares. At 3.3 bundles/sq = 147 bundles of architectural shingles.
💡 Pro tip: Always buy one full extra square (3-4 bundles) beyond your calculated total for ridge cap, starter course, and waste cuts at valleys and hips. Returning unused shingles is easy; running short mid-job can cause dye-lot mismatches.
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Frequently Asked Questions
A roofing square equals 100 square feet of roof surface. All roofing materials are priced by the square. One square of 3-tab shingles needs 3 bundles; architectural shingles typically need 3 to 4 bundles per square.
Standard 3-tab shingles: 3 bundles per square. Architectural/dimensional shingles: 3 to 3.3 bundles per square. Premium designer shingles: up to 4 bundles. Always verify on the package.
Steeper pitches mean more actual surface area than the footprint. A 6:12 pitch adds 12%; a 12:12 adds 41%. Always multiply your footprint by the pitch factor before dividing by 100.
Add 10% for simple gable roofs. Add 15% for roofs with hips and valleys. Add 20% or more for complex cut-up roofs with dormers. Waste accounts for cuts at edges, hips, and valleys.
Measure each roof plane (length x width) from the ground or using satellite tools. Add all planes together, multiply by the pitch factor. The calculator does this automatically.
Use a free smartphone pitch-finder app (accelerometer-based) or estimate from a photo with known reference dimensions. On the roof: hold a 2-foot level horizontal, mark 12 inches along, measure the vertical drop to the surface — that number is the pitch. From the attic: measure rise over a 12-inch horizontal run along a rafter.