A 12 x 12 room with 8 ft walls takes about 17 sheets of 4 x 8 drywall if you're doing walls and ceiling, or 12 sheets for walls only. Both figures assume one door, two windows, and 10 percent waste.
Here's the math, the counts for other room sizes, and the finishing materials that go with them.
The math
Wall area is the room's perimeter times the wall height, minus standard allowances of 21 square feet per door and 15 per window. A 12 x 12 room: 48 ft of perimeter x 8 ft = 384 sq ft, minus one door and two windows = about 333 sq ft. Add the 144 sq ft ceiling for 477, add 10 percent waste, divide by 32 (a 4 x 8 sheet), and round up: 17 sheets.
Sheets by room size (walls + ceiling, 4 x 8 sheets)
| Room | Sheets | Compound (4.5 gal) | Screws |
|---|---|---|---|
| 10 x 10 ft | 13 | 1 | 375 |
| 12 x 10 ft | 15 | 1 | 425 |
| 12 x 12 ft | 17 | 2 | 475 |
| 15 x 12 ft | 20 | 2 | 550 |
| 24 x 24 ft (2-car garage) | 45 | 3 | 1,300 |
The drywall calculator runs any room size, lets you switch to 4 x 10 or 4 x 12 sheets, and counts the joint tape as well.
4x8, 4x10, or 4x12 sheets?
Bigger sheets mean fewer joints to tape and mud, which is why pros hang 12-footers. But a 4 x 12 sheet of half-inch drywall weighs over 80 lb and will not fit in a hatchback, let alone around a stairwell corner. For DIY work, 4 x 8 is the answer unless you have a helper and straight access to the room.
The finishing materials
- Joint compound: about one 4.5 gallon bucket per 450 to 500 sq ft of drywall for a standard three-coat finish. Texturing uses noticeably more.
- Screws: roughly one per square foot with studs at 16 inches on center; buy 1 1/4 inch coarse-thread for wood studs.
- Tape: about 37 ft per 100 sq ft of board. One 500 ft roll covers most single rooms.
- Corner bead: one stick per outside corner, a detail every first-timer forgets.
Two rules that make the job easier
Hang the ceiling first. The wall sheets then push up against the ceiling sheets and support their edges. Rent a drywall lift; it costs little and saves both your back and the board.
Buy a couple of extra sheets. Broken corners and a miscut opening are near-certain on a first job, and 10 percent waste assumes reasonable luck. Leftover drywall stores flat and gets used eventually.
Framing the wall first? The wall framing calculator counts the studs and plates, and the insulation calculator fills the cavities before the board goes up. Painting after? The paint calculator picks up where the mud dries.