Roofing Calculator
Calculate how many roofing squares, shingle bundles, and sheets of underlayment are needed based on roof area and pitch.
ft
ft
%
Roof Area
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Roofing Squares —
Bundles Needed —
How to Use This Calculator
- Enter the roof footprint length and width in feet (the flat ground dimensions, not the slope).
- Select the roof pitch (rise per 12 inches of run).
- Enter the waste percentage and bundles per square.
Formula
Roof area = Footprint area × Pitch factor
Pitch factors: 4/12→1.054, 6/12→1.118, 8/12→1.202, 12/12→1.414
Squares = Roof area ÷ 100 | Bundles = Squares × bundles/square × (1 + waste%)
Example
Example: 30 × 40 ft footprint, 6/12 pitch, 10% waste, 3 bundles/sq → Area 1,342 sq ft → 44 bundles.
Frequently Asked Questions
- One roofing square equals 100 square feet of roof area. Shingles are sold in bundles; typically 3 bundles cover one square.
- Steeper pitches increase the actual surface area relative to the footprint. The calculator multiplies the flat footprint by a pitch factor.
- Most residential roofs have a 4/12 to 6/12 pitch. A 4/12 pitch rises 4 inches for every 12 inches of horizontal run.
- Standard three-tab shingles require 3 bundles per square. Architectural shingles may require 4 bundles per square — check the manufacturer specs.
- Yes — add 10–15% for hip roofs and cuts. The calculator includes a configurable waste percentage.