Roofing Calculator

Turn a roof's footprint and pitch into squares, shingle bundles, ridge cap, starter, drip edge and underlayment.

Include the overhangs.
About 10% for a simple gable, 15% or more for hips and valleys.
Total length that gets ridge cap.
Perimeter for starter strip and drip edge.
3 for most shingles; check the wrapper.
Varies by product.
Synthetic rolls often cover 10 squares.
$
Fractions and decimals both work.
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Squares
Roof area
Shingle bundles
Ridge cap
Starter and drip edge
Underlayment
Shingle Cost

Roof List

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RoofPitchAreaSquaresBundlesCostRemove

How to Figure Roofing Squares and Shingles

Roofing is measured in squares: one square covers 100 square feet of roof. Because a sloped roof is bigger than the ground it covers, multiply the footprint (with overhangs) by the slope factor for the pitch, then add waste for cuts, hips and valleys. Most asphalt shingles come three bundles to a square.

Roof area = footprint × √(pitch² + 144) ÷ 12
Squares = roof area × (1 + waste) ÷ 100   Bundles = squares × bundles per square

Worked Example

Slope Factors

PitchSlope FactorSquares per 1,000 Sq. Ft. of Footprint

Tips

Asphalt shingles need a slope of at least 2/12 under the IRC, with two layers of underlayment between 2/12 and 4/12. Starter strip runs along the eaves (and often the rakes), and drip edge along both. Check the shingle maker's instructions for nailing, starter and ridge cap products, since using theirs can matter for the warranty. Order a bundle or two extra for repairs.