Roofing / Shingle Calculator
Enter your building footprint and roof pitch to get true roof surface area, squares, shingle bundles, underlayment rolls, and nails.
Footprint & Pitch
Materials Needed
Roof area vs. footprint
A roof's actual surface area is always larger than the building's footprint because of the pitch. A 6:12 pitch (6" of rise per 12" of horizontal run) means the roof surface is ~11.8% longer than the horizontal distance. This calculator uses the standard pitch multiplier: for a 6:12 pitch, multiply footprint by ~1.118. Steeper pitches multiply more.
Squares and bundles
Roofing is measured in “squares” — 1 square = 100 square feet of roof surface. Standard 3-tab and architectural shingles come in bundles that cover 33.3 sq ft each, so 3 bundles per square. This calculator returns both.
Underlayment and nails
Synthetic underlayment rolls typically cover 10 squares (1,000 sq ft). Older #15 felt rolls cover 4 squares each. Nails: about 320 nails per square for standard 3-tab (4 nails per shingle), 480 per square for high-wind exposure (6 nails per shingle). A 30 lb box holds roughly 7,200 nails.
What this doesn't include
Ridge caps, hip caps, starter strips, drip edge, ice & water shield for eaves and valleys, flashing, and vent boots. For a real project, add 5–10% material budget beyond the shingle field for these ancillaries, and factor in tear-off + disposal costs.