Roofing Material Calculator

How Roofing Materials Are Calculated

Every material quantity derives from the roof surface area and geometry, with a waste allowance, and is rounded up to whole packages. All calculation parameters (coverage, roll sizes, nail rates) are configurable — they are not hard-coded, because actual product coverage depends on the manufacturer.

Calculation Basis

• Shingles: adjusted squares × 3 bundles/square (at 33.3 sq ft per bundle)
• Underlayment: adjusted area ÷ 400 sq ft per roll
• Starter Strip: 2 × eave length, in 105 ft rolls
• Ridge Cap: ridge length (≈ roof length for a gable roof)
• Drip Edge: roof perimeter, in 50 ft rolls
• Roofing Nails: adjusted squares × 350 nails

Worked Example

50 ft × 30 ft, 1 ft overhang, 6/12 pitch, 10% waste: surface area ≈ 1,860 sq ft → adjusted ≈ 2,046 sq ft ≈ 20.5 squares → about 62 bundles of shingles, 6 rolls of underlayment, 100 ft of starter strip and 7,160 nails.

What You Need

Your roof's length, width and pitch, plus any overhang and the waste factor you want to allow. Accessory quantities depend on packaging — shingle coverage per bundle, underlayment per roll, nail rate and accessory package sizes are drawn from manufacturer specifications and can be adjusted directly on the page.

Assumptions & Limitations

Estimates assume a simple rectangular gable roof. Ridge cap is approximated as the roof length; hips and complex ridgelines need more. Starter strip covers the two eaves only. Full parameter definitions are on our Methodology page.