Generally, you’ll need a screw every 12 inches for 24-inch stud framing and every 16 inches for 16-inch stud framing. On ceilings, you’ll need a minimum of one screw every 12 inches regardless of joist spacing. How many drywall screws or nails you’ll need per sheet depend on the size of the sheet and the spacing of the studs. Screw and nail placements are governed by building codes, which may vary by location.