Most asphalt shingles come three bundles to a square (100 sq ft of roof), so a 25 square roof with 10% waste needs 27.5 squares: 83 bundles of architectural or 3-tab shingles. Heavy designer shingles can run six bundles a square, which doubles the count to 165. Starter, hip and ridge cap and nails are counted from the lengths of your eaves, rakes, ridges and hips.
How shingle bundles are calculated
Take the roof area in squares, add the waste allowance, and multiply by the bundles per square printed on the wrapper. Round up: bundles are sold whole, and a short roof is a second trip.
Bundles = roof squares × (1 + waste %) × bundles per square, rounded up
Worked example with the defaults: 25 squares × 1.10 = 27.5 squares; 27.5 × 3 = 82.5, so 83 bundles. At 64 architectural shingles per square that is 1,760 shingles, and at 4 nails each, 7,040 nails. If you only have the house dimensions, the roofing calculator turns them into squares first.
Bundles per square by shingle type
The numbers come from the manufacturers' own product data. Exposure is how much of each shingle shows; the smaller it is, the more shingles a square takes.
| Shingle | Example product | Size | Exposure | Per square | Bundles per square |
|---|---|---|---|---|---|
| 3-tab | Owens Corning Supreme | 12 × 36 in | 5 in | 80 | 3 |
| Architectural (laminated) | GAF Timberline HDZ, OC Duration | 13¼ × 39⅜ in | 5⅝ in | 64 | 3 |
| Designer (slate look) | Owens Corning Devonshire | 13¼ × 40 in | 5⅝ in | 64 | 3 |
| Designer (luxury) | Owens Corning Woodcrest | 14¼ × 40 in | 4 in | 90 | 6 |
You can check any shingle yourself: width × exposure ÷ 144 is the area one shingle covers. A 3-tab at 36 × 5 in covers 1.25 sq ft, so 80 make a square. The drawing under the calculator lays one square out course by course at the real exposure.
3-tab vs architectural shingles
Both usually come at three bundles per square, so the bundle count is the same. Architectural shingles are larger (64 per square instead of 80) and laminated in two layers for the shadowed look. The price difference shows up in the roof replacement cost calculator: HomeGuide puts installed 3-tab at $3 to $5 per sq ft and architectural at $4 to $6.
Starter shingles, hip and ridge cap
Starter goes along the eaves under the first course so its sealant strip holds the first row down; many wind warranties also want it on the rakes. Measure the eaves (and rakes) in linear feet. TAMKO's Shingle Starter covers 102 ft per bundle, its 10 in Starter 100 ft, and CertainTeed's SwiftStart 116 ft. With 120 ft of eaves and 80 ft of rakes, that is 200 ft of starter: 2 bundles of TAMKO.
Hip and ridge cap covers every ridge and hip. TAMKO lists 3 bundles per 100 lineal ft for its 12¼ × 12 in hip and ridge, about 33⅓ ft a bundle. Cutting your own from 3-tab shingles comes out the same: each shingle gives three 12 in pieces, each laid at 5 in, so 15 in of ridge per shingle and 33⅓ ft per bundle. The default 60 ft of ridge and hips needs 2 bundles.
Nails per square
The IRC (R905.2.6) requires the number of fasteners in the manufacturer's instructions but never fewer than four per strip shingle. Nails must be 12 gauge with a ⅜ in head, long enough to go ¾ in into the deck or through it (R905.2.5). Four nails per shingle is 320 nails per square for 3-tab and 256 for architectural; the default 27.5 squares of 3-tab would take 8,800. Where the bundle wrapper asks for six nails in high-wind zones, change the nails per shingle and the count follows.
Waste: how much extra to order
Waste covers cutting at rakes, hips, valleys and walls, plus the occasional damaged piece. Start near 10% on a simple gable and about 15% on a hip roof or one with valleys and dormers; on a hip roof the angled cuts along every hip add up. Unopened bundles can often be returned, so ordering a bundle or two over is cheaper than running short with a mismatched lot.
Before you order
Confirm the pitch with the roof pitch calculator: asphalt shingles need at least 2/12, and between 2/12 and 4/12 the code asks for a double layer of underlayment. Considering steel instead? Compare the metal roof calculator. New gutters go up after the drip edge; the gutter slope calculator marks the hangers.