Roof Pitch & Area Calculator
Pitch ratio, angle, roof area and shingle squares.
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Roof pitch
6.0:12
26.57° from horizontal · slope factor 1.1180
Add 10–15% for waste, hip and valley cuts, and starter and ridge courses. Complex roofs with dormers waste considerably more than simple gables.
Pitch 6.0:12 · 1,490 sq ft · 14.9 squares
How this is calculated
Roof pitch is expressed as rise over run — how many inches the roof climbs for every 12 inches of horizontal travel. A 6:12 roof rises six inches per foot. Converting that ratio to an angle is straightforward trigonometry:
angle = arctan(rise ÷ run) × 180 ÷ π
Roof area is not the same as the building footprint, because the sloped surface is longer than its horizontal projection. The slope factor accounts for that:
slope factor = √(rise² + run²) ÷ run
roof area = (length + 2 × overhang) × (width + 2 × overhang) × slope factor
Roofing material is sold by the square, where one square covers 100 square feet. Standard three-tab and architectural shingles run about three bundles per square. The figures here cover a simple gable roof; hips, valleys, dormers and ridge caps all add material, so most roofers order 10% extra on a simple roof and up to 15–20% on a cut-up one.