How drywall sheets are calculated
Wall area = 2 × (length + width) × height − doors × 21 − windows × 15
Total = wall area [+ length × width for the ceiling]
Sheets = total × (1 + waste %) ÷ sheet area, rounded up
Openings are deducted as 3 × 7 ft doors and 3 × 5 ft windows. Many hangers deduct only large openings, since cut-outs often become scrap — a waste allowance covers that. Larger sheets mean fewer joints to tape but are heavier to handle.
Worked example
A 14 × 12 ft room with 8 ft walls, one door, two windows, ceiling included, 10% waste:
| Walls (416 − 51) | 365 sq ft |
|---|---|
| Ceiling (14 × 12) | 168 sq ft |
| Total | 533 sq ft |
| With 10% waste | 586 sq ft |
| 4 × 8 sheets | 19 |
Frequently asked questions
How many sheets of drywall for a 12x12 room?
With 8 ft walls and a ceiling, the surface is 528 sq ft before openings — 17 sheets of 4 × 8 without waste, or 11 sheets of 4 × 12.
Should I use 4x8 or 4x12 sheets?
Longer sheets reduce butt joints and taping on long walls. 4 × 8 sheets are easier to carry and fit in smaller vehicles.