How Many Shingle Bundles Per Square?
A roofing square is 100 ft², and three bundles of shingles cover one square. Here is how the math works, where the waste goes, and how to order correctly.
Roofing is quoted in squares, and one square is 100 ft² of roof surface. The standard rule is that three bundles of shingles cover one square. That rule is simple, but the details — waste, starter strips, ridge cap and underlayment — are where estimates go wrong.
The basic math
If a roof has 2,000 ft² of surface area, that is 20 squares. At three bundles per square, the shingle count is 60 bundles. Most three-tab and architectural shingles are packaged so that three bundles cover one square, but always confirm the coverage printed on the bundle, since some products use four bundles per square.
Waste
A simple gable roof with few penetrations wastes about 10 %. A roof with hips, valleys, dormers and multiple planes can waste 12 % to 15 % or more. Waste is not just cut-offs: it includes starter strips, ridge cap, damaged pieces and the shingles that must be cut to fit around vents and flashing.
Starter strips and ridge cap
Starter strips run along the eaves and rakes and are usually ordered separately, though some shingle lines use a cut shingle as the starter. Ridge cap is ordered by the linear foot of ridge and hip, and is typically sold in bundles that cover a stated length. Do not forget these line items when ordering.
Underlayment
Underlayment is ordered by the roll, with coverage stated on the roll. A common 15 lb felt roll covers about 400 ft² (4 squares). Synthetic underlayment rolls often cover more. Add the underlayment as a separate line item and do not assume it is included in the shingle count.
Ordering advice
Order shingles in full bundles, add the waste percentage to the bundle count, and round up. Buy from one dye lot where possible, since color can vary between production runs. Keep one bundle unopened for future repairs. And remember that a quantity estimate is not a structural design: deck condition, fastening and code requirements are separate decisions.