Roofing Calculator
Calculate actual roof area and shingle bundles needed, accounting for pitch.
Assumptions used in this calculation
- Bundle coverage: Assumes standard 3-tab shingles at 3 bundles per 100 sqft (1 roofing square).
About this calculator
A roof's footprint, the flat area you'd measure from a satellite photo, is always smaller than the actual sloped surface a roofer has to cover, and ordering shingles based on footprint alone leads to running short mid-job. This calculator takes the roof's footprint area and its pitch (rise per 12 inches of run), applies the slope factor from the Pythagorean relationship between rise and run to find the true sloped surface area, then converts that into roofing squares (100 sqft units) and standard 3-tab shingle bundles (3 per square) with a waste allowance built in for cuts and overlaps. Instead of separately calculating a slope multiplier and then converting between squares and bundles by hand, one footprint and one pitch value produce a ready-to-order bundle count. The steeper the pitch you enter, the larger the true surface area and bundle count will be, even though the footprint hasn't changed.
Worked example
1500 sqft footprint, 6:12 pitch, 10% waste
Result: ≈ 56 bundles needed
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