How to use the drywall calculator
- Measure the room. Enter the floor length and width and the wall height in feet.
- Decide on the ceiling. Ceilings are usually hung first, often with 1/2 inch sag-resistant board or 5/8 inch board.
- Count doors and windows. Standard openings (21 sq ft per door, 15 sq ft per window) are subtracted. Many pros skip this step on small openings because the offcuts rarely get reused.
- Choose a sheet size. Longer sheets mean fewer seams to tape. 4 × 12 sheets are popular for walls, but are heavy and harder to carry up stairs.
Drywall formula
Total area = wall area + ceiling area − openings
Sheets = total area × (1 + waste %) ÷ sheet area
A 4 × 8 sheet covers 32 sq ft, a 4 × 10 covers 40 sq ft and a 4 × 12 covers 48 sq ft.
Worked example
A 14 × 12 ft bedroom with 8 ft walls has 416 sq ft of walls and a 168 sq ft ceiling, 584 sq ft in total. Subtract one door and one window (36 sq ft) for 548 sq ft. With 10% waste you need 603 sq ft of board, which is 19 sheets of 4 × 8 or 13 sheets of 4 × 12. To finish it, plan on about 550 screws, 203 ft of tape (one 250 ft roll) and 2 buckets of joint compound.
Finishing supplies per 1,000 sq ft
| Item | Typical amount |
|---|---|
| Drywall screws | About 1,000 (roughly 1 per sq ft) |
| Paper joint tape | About 370 ft |
| Ready-mixed joint compound | About 2 to 2.5 buckets of 4.5 gal |
| Corner bead | One 8 or 10 ft piece per outside corner |
Which drywall thickness?
- 1/2 inch: standard for walls in homes.
- 5/8 inch: fire-rated (Type X), used on garage walls shared with the house and often on ceilings.
- Moisture-resistant (green or purple board): bathrooms and laundry rooms, but not inside showers.
- Cement board: behind tile in showers and tub surrounds. Use the tile calculator for the tile itself.
Painting once the drywall is finished? The paint calculator uses the same room measurements. New drywall needs a coat of primer before paint.
Frequently asked questions
How many sheets of drywall do I need for a 12x12 room?
With 8 ft walls and the ceiling, a 12 × 12 room has 528 sq ft of surface. After a door and window and 10% waste, that is about 17 sheets of 4 × 8 drywall.
How many sheets of drywall are in 1,000 square feet?
About 32 sheets of 4 × 8 or 21 sheets of 4 × 12, plus 10% for waste.
How many screws per sheet of drywall?
About 32 screws for a 4 × 8 sheet on walls with studs 16 inches apart, and a few more on ceilings. That works out to roughly one screw per square foot.
Should I subtract windows and doors when estimating drywall?
For large openings like patio doors, yes. For standard doors and windows many installers do not subtract them, since the extra covers waste and cutting mistakes.
How much joint compound do I need?
Plan on about one 4.5 gallon bucket of ready-mixed compound for every 400 to 500 square feet of drywall for a standard three-coat finish.
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Last updated October 2026.