How shingle bundles are calculated
Shingles are sold by the bundle and priced by the square. A square is 100 ft² of roof surface, so start from the roof area, not the floor area. Add waste for cutting at hips, valleys and rakes, then multiply by the bundles per square for your shingle and round up to whole bundles.
squares = roof area ÷ 100
squares with waste = squares × (1 + waste % ÷ 100)
bundles = squares with waste × bundles per square, rounded up
The accessories come from the edge lengths. Starter strip and drip edge run along the eaves and rakes, cap shingles along the hips and ridges, and ice-and-water membrane down the valleys. Underlayment covers the roof area with no shingle waste added.
starter bundles = (eaves + rakes) ÷ 105 ft, rounded up
cap bundles = (hips + ridges) ÷ 33 ft, rounded up
underlayment rolls = roof area ÷ roll coverage, rounded up
drip edge pieces = (eaves + rakes) ÷ 10 ft, rounded up
nails = squares with waste × 320 coil nail weight = nails ÷ 220 per lb
ice-and-water rolls = valleys ÷ 66 ft, rounded up
Shingle weight uses the middle of the typical range for each type: 70 lb per bundle for 3-tab, 77.5 lb for architectural and 87.5 lb for designer shingles. Use it to check the delivery and the roof load if the bundles are stocked on the roof.
Worked example: 1,503 ft² gable roof
The calculator opens on a 1,503 ft² gable roof with architectural shingles, 5% waste, 42 ft of ridge, 84 ft of eaves and 72 ft of rakes. These are the roof area calculator's default results, rounded to whole feet, for a 40 × 30 ft gable at 6/12 with 12 in overhangs (1,503 ft², 84 ft of eaves and 71.6 ft of rakes).
- Squares: 1,503 ÷ 100 = 15.03. With 5% waste: 15.03 × 1.05 = 15.7815 squares.
- Bundles: 15.7815 × 3 = 47.3445, so order 48 bundles.
- Starter: (84 + 72) ÷ 105 = 1.49, so 2 bundles. Hip and ridge cap: 42 ÷ 33 = 1.27, so 2 bundles.
- Synthetic underlayment: 1,503 ÷ 1,000 = 1.50, so 2 rolls. Drip edge: 156 ÷ 10 = 15.6, so 16 pieces.
- Nails: 15.7815 × 320 = 5,050.08, so 5,051 nails. Coil nail weight: 15.7815 × 320 ÷ 220 = about 23.0 lb. Shingle weight: 48 × 77.5 = 3,720 lb.
Choosing a waste factor
Waste covers the shingles you cut off at rakes, hips and valleys, plus the starter course offcuts and a few damaged pieces. The more edges the roof has, the more you cut. Pick the row that fits your roof, or choose Custom and type your own figure.
| Roof | Waste | Bundles for 30 squares |
|---|---|---|
| Simple gable, few penetrations | 5% | 95 |
| Hip roof | 10% | 99 |
| Cut-up roof: valleys, dormers, multiple hips | 15% | 104 |
| Very complex: turrets, many valleys, steep curves | 20% | 108 |
Many suppliers take back unopened bundles, so ask before you order. Rounding up is cheaper than a second delivery for one bundle.
Measuring and ordering tips
- Get the roof area, ridge, hip, eave and rake lengths from the roof area calculator, or from an aerial measurement report if you have one.
- For a dormer, a garage roof or an addition at a different pitch, measure each part on its own and enter it with “+ Add another roof section”. The areas and edge lengths are added together before waste is applied, so the bundles are rounded once for the whole job. Valleys form where the sections meet, so enter their total once under advanced options.
- Rakes are the sloped gable edges. Measure them along the slope, not the level wall below. A hip roof has no rakes, so enter 0.
- 3-tab and most architectural shingles are 3 bundles per square, but some heavy architectural lines are 4. The wrapper states the coverage per bundle.
- Underlayment roll coverage is nominal. Side and end laps reduce what each roll covers, so round up and keep a spare roll on steep or complex roofs.
- Ice-and-water membrane is often also required along the eaves in cold climates. This calculator counts valley rolls only; add eave rolls if your local code or the shingle manufacturer requires them.
- Drip edge laps at joints and corners. If the roof has many short runs, add a piece or two.
Sources
- Owens Corning Supreme 3-tab data sheet: 3 bundles and 80 shingles per square
- GAF Royal Sovereign data sheet: 3 bundles, 79 pieces and 316 nails per square (474 where 6 nails are required)
- Accessory data sheets: Owens Corning ProEdge hip and ridge (33 lin ft per bundle; GAF Seal-A-Ridge 25, CertainTeed Shadow Ridge 30), Owens Corning Starter Strip Plus (105 lin ft), GAF StormGuard ice-and-water (36 in × 66.7 ft, 200 ft²), synthetic underlayment 10 squares per roll
- Waste by roof complexity: estimating rule of thumb; manufacturers give a general 10–15%
- Nail weight: 7,200-count boxes of 1-1/4 in coil roofing nails weigh about 32–33 lb, about 220 nails per lb, so 320 nails ≈ 1.45 lb per square
- Industry convention: 1 roofing square = 100 ft² of roof surface