How many bundles of shingles do I need?
Three bundles cover one square, and one square covers 100 square feet. So bundles = roof area ÷ 100 × 3, plus waste.
The catch is that roof area is not footprint area. A pitched roof is larger than the ground it covers, by a factor of √(1 + (pitch/12)²). A 6/12 roof has a factor of 1.118, so it is 11.8% bigger than its footprint. A 12/12 roof is 41.4% bigger.
Worked example: a 40 × 30 ft building is 1,200 sq ft of footprint. At 6/12 pitch the roof is 1,200 × 1.118 = 1,342 sq ft, which is 13.4 squares. Add 10% waste for 14.8 squares, so 45 bundles.
Common pitch factors: 4/12 = 1.054, 5/12 = 1.083, 6/12 = 1.118, 7/12 = 1.158, 8/12 = 1.202, 10/12 = 1.302, 12/12 = 1.414.
How the calculation works
Pitch factor = √(1 + (rise ÷ 12)²). Roof area = footprint × pitch factor. Squares = area ÷ 100. Bundles = squares × 3 for standard shingles, or 4 for heavier designer profiles.
Measure the footprint including the eave overhang, not the wall line. On a house with 18 in overhangs all round, that adds 3 ft to each dimension — easily a full square on a modest roof.
Waste is 10% on a simple gable roof with no penetrations. Hips, valleys, dormers and skylights each add cuts, and a complex roof can hit 15–20%.
Ridge cap is sold separately and covers roughly 20–25 linear feet per bundle. Starter strip runs both eaves. Nails run about 2.5 lb per square at four nails per shingle, rising to 3.5 lb in high-wind zones requiring six.
Typical roofing material cost, mid-2026
| Material | Unit | Typical range |
|---|---|---|
| 3-tab shingles | per bundle | $26.00 – $38.00 |
| Architectural shingles | per bundle | $33.00 – $50.00 |
| Premium / designer shingles | per bundle | $55.00 – $100 |
| Synthetic underlayment | per 10 sq roll | $90.00 – $180 |
| Ice and water shieldRequired at eaves in cold climates | per 2 sq roll | $70.00 – $140 |
| Ridge cap | per bundle | $40.00 – $75.00 |
| Drip edge | per 10 ft | $9.00 – $18.00 |
| Roofing nails | per lb | $3.00 – $6.00 |
| Installed roof (tear-off included) | per square | $400 – $900 |
Materials are typically a third of an installed roof. Tear-off, disposal, labour and permits make up the rest.
What goes wrong on this job
- Measure the footprint to the drip edge, not the wall. Overhangs are real roof area, and forgetting them is how a job comes up a square short on the last slope.
- Buy all bundles from one production lot. Asphalt shingle colour varies between runs, and a patch from a later lot is visible from the street for the life of the roof.
- Ice and water shield at the eaves is required by code in cold climates — usually 24 in inside the warm wall line. Ice dams are the most common source of winter roof leaks and it is cheap insurance.
- Never lay shingles below 4/12 without the manufacturer low-slope detail, and never below 2/12 at all. Wind-driven rain gets under the courses and the warranty is void.
- Nail placement matters more than nail count. Nails driven above the nailing strip hold nothing, and that single mistake causes most blow-offs in the first big storm.
Frequently asked questions
How many bundles of shingles per square?
Three for standard 3-tab and architectural shingles. Heavier designer profiles need four, and some premium products five — check the wrapper.
How do I calculate roof area from the footprint?
Multiply footprint area by the pitch factor √(1 + (rise/12)²). For a 6/12 roof that is 1.118, so a 1,200 sq ft footprint gives a 1,342 sq ft roof.
How many shingles for a 1,500 square foot roof?
Fifteen squares, so 45 bundles before waste and about 50 with a 10% allowance. Note this is 1,500 sq ft of actual roof surface, not floor area.
How many nails per square of shingles?
About 320 at four nails per shingle, roughly 2.5 lb. High-wind zones require six nails per shingle, which is around 480 nails or 3.5 lb per square.