Convert roof footprint to actual area using pitch and calculate shingle bundles.
Results
The BlockspitchMultiplier = √(1 + (pitch/12)²)actualArea = ⌈footprint × pitchMultiplier⌉ (sq ft)squares = actualArea / 100bundles = ⌈squares × 3 × (1 + waste/100)⌉Ranch House Roof
1,500 sq ft footprint, 6/12 pitch, 12% waste
pitchMultiplier = √(1 + (6/12)²) = 1.118actualArea = ⌈1500 × 1.118⌉ = 1,677 sq ftsquares = 1677 / 100 = 16.8bundles = ⌈16.8 × 3 × 1.12⌉ = 57 bundles