How to calculate it yourself
Roof area = footprint × pitch multiplier. Pitch multipliers: 4/12 = 1.054, 6/12 = 1.118, 8/12 = 1.202, 9/12 = 1.250, 12/12 = 1.414. Bundles = (roof area × 1.10 waste) ÷ 33.3 ft² per bundle, then round up. Add 4-6 bundles for ridge cap and starter strip on a typical home.
Common scenarios
Single-story 1,500 ft² ranch (4/12 pitch)
Roof area = 1,500 × 1.054 = 1,581 ft² + 10% waste = 1,739 ft² = 17.4 squares = 53 bundles + 4 ridge/starter = 57 bundles total. Cost at $40-55/bundle = $2,300-3,150 in shingles alone.
Two-story 2,000 ft² home (footprint 1,400 ft², 6/12 pitch)
Footprint of the actual roof is the upstairs floor, not total ft²: ~1,400 ft² × 1.118 = 1,565 ft² + 10% = 1,722 ft² = 17.2 squares = 52 bundles + 5 cap/starter = 57 bundles. Same as the single-story 1,500 — confusing for first-time DIYers.
Steep colonial 2,500 ft² home (8/12 pitch)
2,500 × 1.202 = 3,005 ft² × 1.10 = 3,306 ft² = 33 squares = 100 bundles + 7 cap/starter = 107 bundles. At this size and pitch, hiring out is almost always smarter — DIY safety on 8/12 needs roof brackets and harness.