{"success":true,"calculator":"roofing","inputs":{"length_ft":40,"width_ft":30,"pitch":"4/12","waste_pct":10},"results":{"footprint_sqft":1200,"roof_area_sqft":1265,"roof_area_with_waste_sqft":1391,"roofing_squares":13.9,"shingle_bundles":42,"underlayment_rolls":4,"ridge_cap_bundles":2},"formula":"Squares = (Length × Width × Pitch_Multiplier × (1 + Waste%)) ÷ 100; Bundles = Squares × 3","notes":"1 square = 100 sq ft. Standard 3-tab shingles: 3 bundles per square."}