How to calculate it yourself
Bundles needed = total roof ft² ÷ 33.3 (round up). For heavyweight shingles divide by 25 instead. Always order an extra bundle or two for ridge and hip caps.
Common scenarios
20-square roof (2,000 ft²)
60 bundles of 3-tab or architectural. Add 4–6 bundles for ridge cap and waste.
Re-roofing a 1,500 ft² ranch
About 1,650 ft² of roof area (1,500 footprint × pitch factor). 50 bundles + 5 for waste = 55 bundles.
Small shed (8×10 ft, 5/12 pitch)
Roof area ≈ 87 ft² ÷ 33.3 = 3 bundles. One full square is the smallest practical order.