How to calculate drywall sheets
- Wall area: add up the length of the walls (the room’s perimeter) and multiply by the wall height.
- Subtract large openings such as doors. Small window cutouts usually end up as waste anyway.
- Add the ceiling (length × width) if you are hanging it.
- Add 10–15% for cuts, then divide by the sheet area and round up.
Worked example: a 12 × 12 ft room with 8 ft walls, walls and ceiling
Walls: 48 ft × 8 ft = 384 sq ft, minus a door (21) and a window (15) = 348 sq ft. Ceiling: 144 sq ft. Total 492 sq ft. With 10% extra that is 541 sq ft, or 16.9 sheets of 4 × 8 (32 sq ft each). Buy 17.
Which sheet size?
| Sheet | Area | Good for |
|---|---|---|
| 4 × 8 ft | 32 sq ft | One person, small rooms, stairs and tight spaces |
| 4 × 10 ft | 40 sq ft | Walls taller than 8 ft, hung vertically |
| 4 × 12 ft | 48 sq ft | Long walls and ceilings: fewer butt joints to finish |
Longer sheets cut finishing time, but a 4 × 12 sheet of ½ in board weighs roughly 60–80 lb, depending on whether it is lightweight board. Ceilings are easier with a panel lift.
Mud, tape and screws
- Joint compound: USG’s all-purpose compound data sheet gives about 9.4 gallons per 1,000 sq ft of board for taping and finishing. A 4.5 gal bucket covers roughly 480 sq ft.
- Tape: about 370 ft per 1,000 sq ft of board. Paper tape is sold in 250 and 500 ft rolls.
- Screws: roughly one per square foot on walls with studs 16 in apart, and a little more on ceilings, where spacing is tighter. Follow the board maker’s schedule.
Once the walls are finished, the paint calculator works out primer and paint for the same room.
Choosing the right board
Use moisture-resistant board in bathrooms and laundry rooms, and cement board behind tile in showers. Many building codes require fire-rated (Type X) board on walls and ceilings shared with an attached garage.