Drywall is quoted per square foot of board, and board covers walls and ceiling. Floor area is a convenient label and a poor proxy, because wall area scales with the room's perimeter while floor area scales with its product.
An 8 × 10 room has 80 ft² of floor and 368 ft² of board. A 16 × 20 room has four times the floor and only 2.3 times the board.
Board area by room
Ceiling height 8 ft throughout, one door and one window deducted per room.
| Room | Floor | Walls | Ceiling | Board area | 4×12 sheets |
|---|---|---|---|---|---|
| 8 × 10 | 80 | 288 | 80 | 368 | 8 |
| 10 × 12 | 120 | 352 | 120 | 472 | 10 |
| 12 × 14 | 168 | 416 | 168 | 584 | 13 |
| 12 × 16 | 192 | 448 | 192 | 640 | 14 |
| 16 × 20 | 320 | 576 | 320 | 896 | 19 |
| 20 × 24 | 480 | 704 | 480 | 1,184 | 25 |
A 4 × 12 sheet is 48 ft². Divide board area by 48 and add roughly 10% for waste and offcuts — the table already includes it.
At 9 ft ceilings, add about 12% to the wall figure; at 10 ft, about 25%.
Materials
| Line | Rate | 12 × 16 room |
|---|---|---|
| 1/2 in board, 4×12 | $17.50 / sheet | $245 |
| Joint compound | $0.06 / ft² | $38 |
| Tape | $0.02 / ft² | $13 |
| Screws | $0.02 / ft² | $13 |
| Corner bead | $2.40 / 8 ft | $24 |
| Materials | $333 |
That is $0.52 per square foot of board, and it varies less than people expect — board is a commodity and the ancillaries are small.
Labor
Hanging and finishing to level 4 runs $1.60–2.80 per square foot of board across most of the country, with metro markets at the top and rural at the bottom.
| Room | Board | Materials | Labor @ $2.10 | Total |
|---|---|---|---|---|
| 8 × 10 | 368 | $191 | $773 | $964 |
| 10 × 12 | 472 | $245 | $991 | $1,236 |
| 12 × 14 | 584 | $304 | $1,226 | $1,530 |
| 12 × 16 | 640 | $333 | $1,344 | $1,677 |
| 16 × 20 | 896 | $466 | $1,882 | $2,348 |
| 20 × 24 | 1,184 | $616 | $2,486 | $3,102 |
Note the shape of it: labor is 78–80% of the job, consistently. Which means shopping for cheaper board saves almost nothing, and the finish level specified — which is a labor decision — moves the total far more than any material choice.
What moves the number
Ceiling height. 9 ft ceilings add 12% to the board and rather more to the labor, because the second row needs staging.
Level 5 finish. Adds $0.40–1.00 per square foot — $256–640 on the 12 × 16 room. Worth it under raking light or gloss paint, and money burned otherwise. The comparison is worth reading before specifying it.
Small rooms cost more per foot. Bathrooms and closets have more corners, more cuts and more linear feet of joint per square foot of board. Expect 15–25% above the rates above, and expect contractors to have a minimum charge that swallows a small room entirely.
Ceilings cost more than walls. Boarding overhead is slower and needs a lift or a second person, and screw spacing is tighter at 12 in.
Removal. Tearing out existing board and hauling it is $0.40–0.90 per square foot on top, and old drywall is heavy — a 4×12 sheet of 1/2 in is 77 lb and a room's worth fills a small trailer.
Deductions
Contractors generally do not deduct openings under about 32 ft² — a standard door is 21 ft² and it gets boarded around, generating offcuts rather than savings. Deducting every opening from an estimate produces a sheet count that comes up short, and how to deduct properly is worth getting right before ordering.
Doing it yourself
Materials only on the 12 × 16 room is $333 against $1,677 — an apparent saving of $1,344, and this is the room size where DIY genuinely makes sense.
What it costs instead is a weekend to hang and three or four evenings of coating and sanding spread over a week, because compound needs 24 hours between coats. The honest DIY comparison puts numbers on that, including the tool purchases people forget.