Roof Pitch & Shingle Calculator

How Roof Pitch Works

Roof pitch is the vertical rise of the roof divided by its horizontal run, traditionally measured over 12 inches.

For a 6/12 pitch, the slope multiplier is √(1 + 0.25) = 1.118. A building with a 1,200 sq ft footprint will have an actual roof surface area of 1,200 × 1.118 = 1,341.6 sq ft.

Roofing Squares & Bundles Rule

• 1 Roofing Square = 100 sq ft: This is the universal construction unit for roofing materials.
• 3 Bundles per Square: The vast majority of standard asphalt architectural shingles come in 3 bundles per square.
• Minimum Pitch for Shingles: Asphalt shingles require a minimum 2:12 pitch with double underlayment, or 4:12 with single underlayment to prevent wind-driven rain penetration.
• Waste Factor: Always order at least 10% extra for simple gable roofs and 15% to 20% for hip roofs with valleys and hips where angled shingle cuts are discarded.