Estimate roof area from a house's footprint and roof pitch, plus roof squares needed and an optional cost estimate.
Roof pitch is the rise over a 12-inch run — a 6/12 pitch rises 6 inches for every 12 inches horizontally. Because a pitched roof's actual surface is longer than its flat footprint, the base area is multiplied by a slope factor: √((rise/12)² + 1). A steeper pitch means more roofing material for the same footprint.
This estimate uses the house's footprint area and pitch only — it doesn't account for eave overhang or the exact number of material bundles/rolls, both of which depend on the roof's specific shape and layout. For a more precise material list, measure each roof section individually (our Area Calculator can help) and consult your roofing supplier.
Convert with rise = 12 × tan(angle). For example, a 25° angle is roughly a 5.6/12 pitch.
Treat it as a planning estimate. Always confirm quantities with an on-site measurement or a roofing contractor before ordering.
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