Roofing Calculator

First calculate roof area using plan area × pitch multiplier. A 1,500 sq ft footprint with 6:12 pitch (multiplier 1.12) = 1,680 sq ft. Divide by 100 to get 'squares' (roofing measurement unit). Add 10-15% for waste.

A square equals 100 square feet of roof coverage. It's the standard ordering unit for roofing materials. A bundle of shingles typically covers 1/3 of a square (33.3 sq ft), so 3 bundles = 1 square.

Steeper roofs have more surface area. A 12:12 pitch roof has 41% more area than the footprint, while a 4:12 pitch adds only 5%. The calculator uses pitch multipliers to convert plan area to actual roof area.

Add 10% for simple gable roofs, 15% for hip roofs with valleys, and 20% for complex roofs with multiple dormers. High-quality shingles have less waste than 3-tab shingles due to alignment requirements.

Standard roofing requires one layer of felt (15 lb or 30 lb) or synthetic underlayment. In cold climates, add ice and water shield for the first 3-6 feet from eaves. The calculator estimates underlayment rolls needed.

Standard shingle installation requires 4-6 nails per shingle, roughly 2-2.5 lbs of nails per square. High-wind areas require 6 nails per shingle. The calculator estimates nail quantities based on your location.