Shingle Bundles
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Most standard asphalt shingles are packaged so that 3 bundles cover one roofing square (100 square feet), though some heavier architectural shingles use 4 or 5 bundles per square — always check the specific product's coverage rating rather than assuming 3.

A square is simply 100 square feet, a trade convention that makes estimating and quoting roofing jobs faster — dividing total roof area by 100 gives the number of squares, which then converts directly to bundle count using the product's bundles-per-square rating.

It needs the actual sloped roof area, not the flat footprint — since shingles cover the true roof surface, which is larger than the footprint due to pitch, you should run the pitch-adjusted area calculation first and use that result as the input here.

A common allowance is 10% for simple gable roofs and up to 15-20% for roofs with many hips, valleys, or dormers, since these features require more cuts and produce more offcuts. Ridge cap shingles are often calculated and ordered separately from the field shingle bundle count.

Always round up to the next whole bundle, since shingles are sold by the bundle and a partial bundle can't be purchased — and because bundle counts are usually already padded with a waste factor, rounding up rarely causes meaningful overordering.