How many sheets of drywall do I need?
Add up the wall area, subtract doors and windows, add 10% for waste and divide by the area of one sheet. A 12 × 14 ft room with 8 ft walls, one door and two windows needs 13 sheets of 4 × 8 drywall for the walls, or 19 sheets with the ceiling.
Worked example: a 12 × 14 ft bedroom
- Wall area: 2 × (12 + 14) × 8 = 416 sq ft.
- Subtract openings: 1 door × 20 + 2 windows × 15 = 50 sq ft, leaving 366 sq ft.
- Add 10% waste: 366 × 1.10 = 402.6 sq ft.
- Sheets: 402.6 ÷ 32 = 12.6, rounded up to 13 sheets of 4 × 8.
- With the 168 sq ft ceiling added, the room needs 19 sheets.
Drywall sheets by room size
Rooms with 8 ft walls, one door and two windows, 4 × 8 sheets and 10% waste.
| Room | Walls only | Walls and ceiling |
|---|---|---|
| 10 × 10 ft | 10 | 13 |
| 12 × 12 ft | 12 | 17 |
| 12 × 14 ft | 13 | 19 |
| 14 × 16 ft | 15 | 23 |
| 16 × 20 ft | 19 | 30 |
How the calculator works
Wall area = 2 × (length + width) × wall height
Net area = wall area + ceiling area − (doors × 20) − (windows × 15)
Sheets = net area × (1 + waste %) ÷ sheet area, rounded up
A 4 × 8 sheet covers 32 sq ft, a 4 × 10 sheet 40 sq ft and a 4 × 12 sheet 48 sq ft. Vertigraph recommends adding 10% to 15% for waste; use the higher figure for rooms with many openings, short walls or angles.
Larger sheets mean fewer seams to tape, but they are heavier and harder to carry and lift. Many DIYers stick with 4 × 8 sheets for that reason.
Frequently asked questions
How many square feet is a sheet of drywall?
A 4 × 8 sheet covers 32 sq ft, a 4 × 10 sheet covers 40 sq ft and a 4 × 12 sheet covers 48 sq ft.
How many sheets of drywall do I need for a 12 × 12 room?
With 8 ft walls, one door, two windows and 10% waste, the walls take 12 sheets of 4 × 8 drywall. Adding the ceiling brings it to 17 sheets.
How much extra drywall should I buy?
Add about 10% for a simple rectangular room and up to 15% for rooms with many openings, angles or short walls.
Should I subtract doors and windows?
Yes. This calculator subtracts 20 sq ft per door and 15 sq ft per window. Offcuts from openings are often too small to reuse, so the waste allowance stays the same.
Sources
- Vertigraph, How to Calculate Drywall Square Footage