Roofing Calculators
Roofing is sold in squares and bundles, measured in slopes and pitches. This calculator converts your roof's footprint and pitch into the bundle count a supplier will quote you.
Roofing Shingle Calculator
Shingle bundles and squares for your roof.
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Squares, bundles and the pitch factor
Roofers don't measure in square feet. They measure in squares, where one square is 100 sq ft of roof surface, and shingles arrive in bundles: three bundles to a square for standard shingles, four or five for heavyweight architectural products. The Roofing Shingle Calculator converts your roof into both numbers, waste included.
The catch is that a roof's surface is bigger than the house's footprint, because slopes are longer than the ground they cover. Roofers correct with a pitch factor, √(1 + (rise ÷ 12)²), so a 6/12 roof has about 11.8% more surface than its footprint and a steep 12/12 roof about 41% more. Measure the footprint including the eaves overhangs, pick the pitch, and the calculator applies the exact factor rather than a rounded table value. Waste runs about 10% on a simple gable roof and 15% once hips, valleys and dormers start cutting shingles. Related work for a roof-over project: gutters and ventilation are sized separately, and any structural lumber comes from the lumber calculators.
Frequently asked questions
How many bundles of shingles are in a square?
Three for standard shingles. A bundle covers about 33 sq ft, and a square is 100 sq ft. Heavyweight and architectural shingles are thicker, so a bundle covers less: plan on four or five bundles per square for those, as the calculator's options reflect.
How do I measure my roof without climbing on it?
Measure the house footprint (including eaves overhangs) from the ground and multiply by the pitch factor for your roof's slope. At 4/12 the factor is 1.054; at 6/12, 1.118; at 8/12, 1.202. The calculator applies it for you and adds waste.
How much waste should I add for shingles?
About 10% for a simple gable roof, 15% for a cut-up roof with hips, valleys and dormers. The allowance covers cuts, starter courses and the occasional damaged bundle.