The formula
Wall area = 2 × (length + width) × height − doors × 20 − windows × 15 Ceiling area = length × width Sheets = total area × 1.10 ÷ sheet area (32, 40 or 48 sq ft)
Example: a 12 × 14 ft room with 8 ft walls, a door and a window has 381 square feet of wall plus 168 square feet of ceiling, 549 square feet in all. With 10% extra that is 19 sheets of 4 × 8.
Quick answers for common rooms
| Room, 8 ft walls | Walls only | Walls and ceiling |
|---|---|---|
| 10 × 10 ft | 10 | 14 |
| 10 × 12 ft | 11 | 16 |
| 12 × 12 ft | 12 | 17 |
| 12 × 14 ft | 14 | 19 |
| 14 × 16 ft | 16 | 23 |
Which sheets to buy
- 4 × 8 sheets are the easiest to carry and fit in most vehicles.
- 4 × 10 and 4 × 12 sheets mean fewer seams to tape on long walls.
- 1/2 inch is standard for walls; 5/8 inch is common on ceilings and where fire-rated walls are required.
For screws, plan on roughly one per square foot of drywall, about 32 for a 4 × 8 sheet.
Questions
How many sheets of drywall do I need for a 12 × 12 room?
With 8-foot walls, one door and one window, about 12 sheets of 4 × 8 for the walls, or 17 with the ceiling.
How many screws per sheet of drywall?
About 32 for a 4 × 8 sheet on walls, a few more on ceilings where screws go closer together.
Should I subtract windows and doors?
Yes for estimating, as this calculator does, but keep the 10 percent extra: cut-outs rarely save whole sheets.