Roofing is measured in squares: one square covers 100 sq ft of roof surface. Shingles are sold in bundles, and for most asphalt shingles three bundles make a square, although some heavier products take four or more. This chart turns a house footprint and roof pitch into squares and bundles, and the sections below cover what changes the count: pitch, waste, the bundles-per-square figure on the wrapper, starter and ridge pieces, nails and underlayment. For a roof of your exact size, use the roofing calculator.
Shingle bundles by house size and pitch
| Footprint incl. overhangs | 4/12 pitch | 6/12 pitch | 8/12 pitch | 10/12 pitch | 12/12 pitch |
|---|---|---|---|---|---|
| 1,000 sq ft | 11.6 sq / 35 bdl | 12.3 sq / 37 bdl | 13.2 sq / 40 bdl | 14.3 sq / 43 bdl | 15.6 sq / 47 bdl |
| 1,200 sq ft | 13.9 sq / 42 bdl | 14.8 sq / 45 bdl | 15.9 sq / 48 bdl | 17.2 sq / 52 bdl | 18.7 sq / 57 bdl |
| 1,500 sq ft | 17.4 sq / 53 bdl | 18.4 sq / 56 bdl | 19.8 sq / 60 bdl | 21.5 sq / 65 bdl | 23.3 sq / 71 bdl |
| 1,800 sq ft | 20.9 sq / 63 bdl | 22.1 sq / 67 bdl | 23.8 sq / 72 bdl | 25.8 sq / 78 bdl | 28.0 sq / 85 bdl |
| 2,000 sq ft | 23.2 sq / 70 bdl | 24.6 sq / 74 bdl | 26.4 sq / 80 bdl | 28.6 sq / 86 bdl | 31.1 sq / 94 bdl |
| 2,500 sq ft | 29.0 sq / 87 bdl | 30.7 sq / 93 bdl | 33.1 sq / 100 bdl | 35.8 sq / 108 bdl | 38.9 sq / 117 bdl |
| 3,000 sq ft | 34.8 sq / 105 bdl | 36.9 sq / 111 bdl | 39.7 sq / 119 bdl | 43.0 sq / 129 bdl | 46.7 sq / 141 bdl |
Why the footprint is not the roof area
A sloped roof has more surface than the floor area it covers. The pitch factor, √(1 + (rise ÷ 12)²), converts plan area to roof area: a 6/12 roof has about 12% more surface than its footprint, a 12/12 roof about 41% more. Measure the footprint to the outside of the overhangs, not the walls, because the shingles cover the eaves and rakes too. A 1 ft overhang around a 30 x 40 ft house adds 144 sq ft of plan area before pitch is applied.
| Pitch | Pitch factor | Extra over footprint |
|---|---|---|
| 3/12 | 1.031 | 3% |
| 4/12 | 1.054 | 5% |
| 5/12 | 1.083 | 8% |
| 6/12 | 1.118 | 12% |
| 7/12 | 1.158 | 16% |
| 8/12 | 1.202 | 20% |
| 9/12 | 1.250 | 25% |
| 10/12 | 1.302 | 30% |
| 12/12 | 1.414 | 41% |
Bundles per square: read the wrapper
The number of bundles per square depends on the product, not on the roof. In one maker’s guide specification, every architectural (laminated) shingle in the range measures 13-1/4 x 39-3/8 in, is laid at a 5-5/8 in exposure and needs 64 shingles to cover a square of 98.4 sq ft, yet some lines are packed as 3 bundles of 20 or 22 shingles and the heavier lines as 4 bundles of 16. The coverage is the same; only the packing differs. Older three-tab shingles (12 x 36 in at a 5 in exposure) need 80 pieces per square. Always take the bundles-per-square figure from the wrapper or the product data sheet of the shingle you are buying.
Waste, starter and ridge
- Waste: about 10% on a plain gable roof, 15% or more with hips, valleys, dormers and skylights, because of the cut pieces at every edge.
- Starter strip: a row along every eave (and usually the rakes) under the first course. Measure the eave and rake length and buy starter shingles by linear feet of coverage per bundle.
- Hip and ridge cap: measured in linear feet of hips and ridges; coverage per bundle is printed on the bundle and varies widely by product.
- Drip edge: the guide specification calls for drip edge on all roof edges, installed under the underlayment at the eaves and over it at the rakes, with joints lapped at least 2 in.
Nails per square
The IRC requires asphalt shingles to have the number of fasteners the manufacturer specifies, and not fewer than four per strip shingle (R905.2.6). With 64 laminated shingles per square that is at least 256 nails, or 384 where six-nail application is required for high-wind areas; with 80 three-tab shingles it is 320 or 480. The guide specification calls for galvanized, stainless or aluminium roofing nails of at least 12 gauge (0.0808 in shank) with a 3/8 in head, long enough to penetrate at least 3/4 in into the wood deck or fully through thinner sheathing. In practice that means 1-1/4 in nails for a new roof over 7/16 or 1/2 in sheathing, longer for a second layer.
Underlayment and ice barrier
- Minimum slope: asphalt shingles are allowed only on roofs of 2/12 or steeper, and slopes from 2/12 up to 4/12 need two layers of underlayment (IRC R905.2.2 and R905.1.1).
- Ice barrier: where there has been a history of ice forming along the eaves, the IRC requires an ice barrier from the eave edge up to a point at least 24 in inside the exterior wall line (R905.1.2). The guide specification uses a full 36 in roll at the eaves, extended as needed to reach that point.
- Valleys and penetrations: self-adhering membrane at least 36 in wide centred in valleys, and pieces around vent pipes, chimneys and along walls before the underlayment and flashing.
- Rolls: felt and synthetic underlayments cover different areas per roll; divide the roof area by the coverage printed on the roll and add about 10% for laps.
Worked example: 1,500 sq ft footprint at 6/12
1,500 × 1.118 = 1,677 sq ft of roof, or 16.8 squares. Add 10% waste for a simple roof: 18.4 squares. With 3-bundle shingles that is 56 bundles; with 4-bundle shingles, 74. Nails at 4 per shingle: about 4,723 for laminated shingles. Bundles are heavy: check the weight printed on the wrapper and ask for the delivery to be spread along the ridge rather than stacked in one place.
Frequently asked questions
How many bundles of shingles are in a square?
Usually 3 for standard asphalt shingles; some heavier architectural and designer shingles are packed 4 or more to a square. The wrapper states it.
How many square feet does a square of shingles cover?
100 sq ft by definition. Maker coverage figures are often slightly less, such as 98.4 sq ft per square in the specification we cite.
How many bundles of shingles for 1,500 sq ft?
For 1,500 sq ft of roof surface, 15 squares plus 10% waste = 16.5 squares = 50 bundles at 3 per square. For a 1,500 sq ft footprint at 6/12 pitch, about 56 bundles.
How do I convert roofing squares to square feet?
Multiply by 100: 25 squares = 2,500 sq ft of roof surface.
Sources
- Owens Corning, fiberglass-based asphalt shingle guide specification, Section 07 31 13 (cached copy): shingle size 13-1/4 x 39-3/8 in, exposure 5-5/8 in, 64 shingles and 98.4 sq ft per square, 3 or 4 bundles per square by product, ice and water barrier and fastener requirements.
- International Code Council, 2021 International Residential Code (IRC). Requirements are paraphrased with their section numbers; local codes and amendments may differ, so confirm with your building department. Sections R905.1.1 (underlayment), R905.1.2 (ice barrier), R905.2.2 (slope), R905.2.6 (fasteners).
Last reviewed: 24 October 2026. Numbers in the tables are our arithmetic from the sources listed; code sections are summarised, not quoted. How we check our work: methodology and corrections. Spotted an error? Please let us know.