This roofing calculator turns your building size, roof pitch and overhang into roof area, roofing squares and the number of shingle bundles to buy, with waste included.
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With a 1 ft overhang the roof surface is 1,502.6 ft². Adding 10% waste gives 16.5 squares, which is 50 bundles at 3 per square.
Roofing needed, including waste
16.5 squares
Inputs
Results are estimates for planning only. Supplier specifications, product yields, site conditions and local codes vary. Confirm quantities with your supplier or a qualified professional before you buy or build.
From building size, building length 40 ft, building width 30 ft, eave overhang 1 ft, roof pitch 6 /12, bundles per square 3 bundles, underlayment per roll 400 ft².
Roofing needed, including waste
16.5 squares
From building size, building length 12 m, building width 9 m, eave overhang 0.3 m, roof pitch 27 °, bundles per square 3 bundles, underlayment per roll 40 m².
Roofing needed, including waste
16.1 squares
From building size, building length 36 ft, building width 24 ft, eave overhang 1 ft, roof pitch 4 /12, bundles per square 3 bundles, underlayment per roll 400 ft².
Roofing needed, including waste
11.5 squares
I know the roof area, roof surface area 2400 ft², bundles per square 3 bundles, underlayment per roll 400 ft².
Roofing needed, including waste
27.6 squares
Multiply the footprint (including overhang) by the multiplier to get roof surface area.
| Pitch | Angle | Multiplier | Roof area for 1,000 sq ft footprint |
|---|---|---|---|
| 3/12 | 14.0° | 1.031 | 1,031 sq ft |
| 4/12 | 18.4° | 1.054 | 1,054 sq ft |
| 5/12 | 22.6° | 1.083 | 1,083 sq ft |
| 6/12 | 26.6° | 1.118 | 1,118 sq ft |
| 7/12 | 30.3° | 1.158 | 1,158 sq ft |
| 8/12 | 33.7° | 1.202 | 1,202 sq ft |
| 9/12 | 36.9° | 1.250 | 1,250 sq ft |
| 10/12 | 39.8° | 1.302 | 1,302 sq ft |
| 12/12 | 45.0° | 1.414 | 1,414 sq ft |
With 10% waste and 3 bundles per square.
| Roof surface area | Squares | Squares with waste | Shingle bundles |
|---|---|---|---|
| 1,000 sq ft | 10.0 | 11.0 | 33 |
| 1,500 sq ft | 15.0 | 16.5 | 50 |
| 2,000 sq ft | 20.0 | 22.0 | 66 |
| 2,500 sq ft | 25.0 | 27.5 | 83 |
| 3,000 sq ft | 30.0 | 33.0 | 99 |
| 4,000 sq ft | 40.0 | 44.0 | 132 |
A roof is bigger than the building under it. The slope adds area, and the eaves add more, so measuring the floor plan alone will leave you short. The pitch multiplier in the calculator accounts for the slope, and the overhang field accounts for the eaves.
Roofing is sold in squares, where one square covers 100 square feet. Shingles are packed in bundles, usually three to a square, although some heavier products use four. Check the packaging for the product you plan to buy. For a deck or porch roof, compare with the flooring calculator for the surface below, and use the paint calculator for fascia and trim.
You can measure most roofs from the ground. Measure the length and width of the building and add the overhang at the eaves, which you can usually estimate from the ground by sighting up from the wall. For pitch, measure from an attic rafter, or use a phone app held against the underside of a rafter, instead of climbing onto the roof.
If the roof has several planes, such as a main roof with a garage or an extension, calculate each section separately and add the surface areas, then use the "I know the roof area" option. Treat dormers and valleys as extra waste.
Shingles are the biggest line item, but the job also needs underlayment, starter strips along the eaves, ridge caps along the ridge and hips, drip edge, flashing around chimneys and vents, and nails. Ask your supplier to total these from the same measurements.
Roofing is hard to match later, so buy from the same production lot when you can, and keep a few spare bundles for repairs. Roofing is also risky work, so for anything steep, high or complex, hire a qualified roofer.
Divide the roof surface area by 100 square feet. A 1,500 square foot roof surface is 15 squares, or 16.5 squares with a 10% waste allowance.
Usually three, though some products use four. Check the packaging, then enter the number in the calculator.
Pitch is the rise over 12 inches of horizontal run. Place a level 12 inches out from the roof surface and measure the vertical distance up to the roof. If that is 6 inches, the pitch is 6/12. Many phone apps also measure slope angle.
About 10% for a simple gable roof. Hip roofs, valleys, dormers and many cuts push waste to 15% or more. Ask your supplier or installer for a figure that suits your roof.
Yes. The overhang you enter is added to each side of the building before the pitch multiplier is applied. Enter 0 if you are measuring the roof itself.
With a 6/12 pitch, a 1 ft overhang and 10% waste, about 50 bundles, or 16.5 squares.
Small openings do not change the quantity much, and the waste allowance covers them. Subtract very large openings by working the roof out in sections.
The number of individual shingles varies by product and style. What matters for ordering is coverage. With three bundles per square, one bundle covers about 33 square feet. Check the packaging for your shingle.
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