Estimate how many 4x8 or 4x12 drywall sheets you need for a room, including ceiling and waste.
Wall area = perimeter × height; add ceiling area if needed. A 4x8 sheet covers 32 sq ft and a 4x12 covers 48 sq ft. Leave doors and windows in as your waste buffer, or subtract them yourself.
Many pros do not; the offcuts cover waste.
4x12 means fewer seams but is heavier to handle.