How many bundles of shingles do I need for a 40 × 30 ft roof at 6/12 pitch?
For the worked example (40 × 30 ft plan, 6 in 12 pitch, 3 bundles per square, 10% extra) the material list is Shingle bundles: 45 bundles (calculated 14.76 squares × 3 per square = 44.27 bundles, based on 3 bundles per square, 10% extra). Quantities to buy are whole units rounded up from the calculated amounts. Enter your own measurements in the calculator above for your exact list.
How to use this calculator
- Choose how to enter the roof: a measured surface area, or plan dimensions and a pitch.
- For plan dimensions, measure from above, level, including the overhang you will cover. Enter the rise and run of the pitch.
- Enter how your shingle lists its coverage: the installed coverage per bundle (exact), or the bundles per roofing square. Keep or change the extra allowance.
- Optionally add the coverage per roll of your underlayment, then copy, print or share the list.
How this is calculated
- Roof surface area = plan area × √(1 + (rise ÷ run)²) for one uniform pitch, or the area you enter
- Roofing squares = roof area ÷ 100 sq ft
- Bundles = round up (roof area × (1 + allowance ÷ 100) ÷ installed coverage per bundle)
- Equivalent when listed per square: round up (squares × (1 + allowance ÷ 100) × bundles per square)
- Underlayment rolls = round up (roof surface area ÷ installed coverage per roll)
Geometry is deterministic. Material coverage, density, installation waste and product yield can vary. We expose those assumptions so you can replace them with the values printed on the products you are actually buying. Treat every result as an estimate. Items on your list are labelled Calculated (straight from your measurements) or Estimated (depends on an assumption), and “Buy” quantities are whole units rounded up.
Sources
- TAMKO – Top 4 Factors That Affect the Cost of a New Roof. One square of shingles covers 100 sq ft of roof; three bundles per square is a rule of thumb for most three-tab and laminated shingles. We use the 100 sq ft square. Bundles per square is entered by you because it varies by product.
Last reviewed: . See the methodology.
Assumptions
These starting values are used until you change them. They are typical, not universal. Check the label on the product you are buying.
| Assumption | Starting value | Where it comes from |
|---|---|---|
| Roofing square | 100 sq ft | Manufacturer / industry sourced – The area one “square” of shingles covers, per TAMKO. |
| Slope multiplier | √(1 + (rise ÷ run)²) | Mathematical – Roof surface area ÷ plan area for one uniform pitch |
| Extra allowance | 10% | Common planning default |
| Bundles per roofing square | You enter it | You enter it (product / supplier) |
| Installed coverage per bundle | You enter it | You enter it (product / supplier) |
| Underlayment coverage per roll (optional) | You enter it | You enter it (product / supplier) |
Worked example
A 40 × 30 ft plan at a 6 in 12 pitch, 3 bundles per square and 10% extra:
- Shingle bundles: 45 bundles (14.76 squares including extra) · 3 bundles per square, 10% extra
Common questions
How many bundles are in a square?
It depends on the shingle. Three is a common rule of thumb for many three-tab and laminated shingles, but some products use more. Enter the number printed on your bundle, or choose coverage per bundle if that is how it is listed.
Is a roofing square always 100 sq ft?
As a measuring unit, yes. A product’s own listed coverage can differ slightly (some data sheets list 98.4 sq ft for three bundles), so use coverage per bundle when you have it. The extra allowance is for cutting and waste, not for that difference.
Why does pitch change the area?
A sloped roof is larger than its plan view. The multiplier is the slope length for each unit of run. It applies to a roof plane at one pitch.
Does it work for complex roofs?
Not by itself. Dormers, valleys and several pitches need each plane measured, or the measured surface area entered directly.
Guides
- How Many Bundles of Shingles Do I Need?Roof area plus allowance, divided by one bundle's coverage, rounded up.
- What Is a Roofing Square?100 sq ft of roof surface, and how pitch and product turn squares into bundles.
- How Much Siding Do I Need?Wall and gable area, large openings, allowance, then squares or cartons.
- What Is a Square of Siding?100 sq ft: the siding ordering unit, and how it differs from area and cartons.