Roofing Calculator
Estimate roofing materials for your project. Enter your building's footprint dimensions and roof pitch to get the roof area, number of squares, and shingle bundles needed.
Rise over 12 inches of horizontal run
About the Roofing Calculator
This roofing calculator estimates the total roof surface area and material quantities for a gable or hip roof. The footprint area (length × width) represents the ground area covered by the building. The roof area is always larger than the footprint because the roof is sloped — the pitch multiplier converts the flat footprint area to the actual sloped surface area. A 6:12 pitch means the roof rises 6 inches for every 12 inches of horizontal run, giving a pitch multiplier of 1.118. To measure your building's footprint area accurately, the Square Footage Calculator supports rectangles and other shapes.
A roofing square equals 100 square feet. Most standard three-tab asphalt shingles require 3 bundles per square; architectural shingles may require 4. The waste factor accounts for cut pieces at hips, valleys, rakes, and ridges. Use 10% for a simple gable roof with few cuts, 15% for moderate complexity, and 20% for roofs with many hips, valleys, or steep pitches. If you're also pouring concrete footings or a foundation as part of your project, the Concrete Calculator will help estimate how many bags or cubic yards you need.
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For a related calculation, use Tile Calculator to calculate tiles and boxes needed for any room. Includes waste percentage and fixture subtraction. Alternatively, use Stair Calculator to calculate riser height, tread depth, and stringer length. Check IRC building code compliance.