Roofing Calculator
Estimate roofing materials from the building footprint and roof pitch. Get roof area, squares, shingle bundles, and underlayment.
Results
Enter your measurements to see an estimate.
Calculated: — EasyBuildTools, www.easybuildtools.com
How to use the undefined
Enter the building footprint (length and width) and the roof pitch as rise per 12 inches of run. The pitch converts the flat footprint into the true sloped area. Set the coverage per roofing square (100 sq ft is standard) and a waste allowance. The tool estimates squares, shingle bundles, and underlayment rolls.
Formula and methodology
Footprint = length × width. Slope factor = √(pitch² + 144) ÷ 12. Roof area = footprint × slope factor. Adjusted = area × (1 + waste%/100). Squares = adjusted ÷ 100. Bundles = squares × 3 (three bundles per square). Underlayment rolls ≈ adjusted ÷ 400.
Worked example
Roof: 40 ft × 30 ft footprint, 6:12 pitch, 10% waste. Slope factor = √(36+144)÷12 ≈ 1.118. Area = 1200 × 1.118 = 1342 sq ft, with waste 1476 = 14.8 squares, about 45 bundles. Enter the values above to confirm.
Helpful measurement tips
- Steeper pitches add significant area — do not estimate from the footprint alone.
- Hips, valleys, and complex shapes increase waste; raise the allowance.
- Order starter and ridge caps separately from field shingles.