How many USG Sheetrock panels do I need?
Work out the area to board - the walls (room perimeter × ceiling height) plus the ceiling if you are boarding it - then divide by the panel area and add wastage. A 12 × 12 ft room with 8 ft ceilings and the ceiling boarded is about 528 sq ft; with 4 × 8 ft panels (32 sq ft each) and 10% wastage that is 19 panels. Enter your room above for the exact count.