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How many drywall sheets do I need for a room?

Short answer: Add the wall and ceiling area, subtract doors and windows, add 10–15% waste, then divide by the sheet size: 32 sq ft for a 4×8 sheet or 48 sq ft for a 4×12. A 12×12 room with 8-ft walls, a ceiling, one door and one window is 493 sq ft, which is 17 sheets of 4×8.

The formula

Wall area = 2 × (length + width) × height
Ceiling area = length × width
Net area = walls + ceiling − 20 sq ft per door − 15 sq ft per window
Sheets = net area × (1 + waste) ÷ sheet area, rounded up

Use 10% waste for simple rectangular rooms and 15% for rooms with many openings, angles or soffits.

Worked example

12 × 12 room, 8-ft walls, ceiling included, 1 door, 1 window, 4×8 sheets, 10% waste:

• Walls: 2 × (12 + 12) × 8 = 384 sq ft
• Ceiling: 12 × 12 = 144 sq ft
• Net: 384 + 144 − 20 − 15 = 493 sq ft
• Sheets: 493 × 1.10 ÷ 32 = 16.9 → 17 sheets

FAQ

Should I subtract doors and windows?

For estimating, yes for full-size doors and large windows. Small openings usually come out of a sheet you buy anyway, which is why the waste factor matters.

4×8 or 4×12 sheets?

4×12 sheets mean fewer butt joints and less taping on long walls, but they are heavy for one person. Use 4×8 if you are hanging alone or carrying sheets up stairs.

How much joint compound do I need?

Plan roughly one 4.5-gallon bucket of all-purpose compound for about every 8 sheets for taping and two finish coats. See the drywall guide for tape and screws.