Roofing Calculator — Shingle Bundles & Squares
Spec no. 15How to use
Measure the length and width of the roof footprint (the building footprint plus overhangs). Enter the roof pitch as rise per 12 inches of run — the multiplier sqrt(1 + (rise/12)²) converts footprint to actual sloped area. Squares = area ÷ 100, bundles = squares × 3 (three bundles cover one square), and one roll of underlayment covers about 4 squares.