How to use the drywall calculator
- Enter the room's length, width and wall height, plus the number of doors and windows. Tick "Include the ceiling" if you're hanging it too.
- Pick a sheet size. Longer sheets mean fewer seams to tape, but they're heavier and harder to get through doors and up stairs.
- Keep 10% extra for cut-offs. Bump it to 15% for rooms with lots of openings or angles.
Drywall formula
area = 2 × (length + width) × height + ceiling − openings
sheets = area × (1 + waste %) ÷ sheet area
The calculator subtracts 21 sq ft per door and 15 sq ft per window. Many pros subtract little or nothing for openings, because the cut-outs rarely produce usable pieces; set waste higher if you want that margin.
Finishing materials rule of thumb
- Screws: about 32 per 4 × 8 sheet on walls (more on ceilings), roughly 1 screw per sq ft.
- Joint compound: about 138 lb of ready-mixed all-purpose compound per 1,000 sq ft, or roughly one 4.5 gallon bucket per 450 sq ft.
- Paper tape: about 370 ft per 1,000 sq ft of drywall.
Sheets needed for common rooms
| Room | Area (sq ft) | 4 × 8 sheets | 4 × 12 sheets |
|---|---|---|---|
| 10 × 10 ft, 8 ft walls | 320 | 11 | 8 |
| 10 × 12 ft, 8 ft walls | 352 | 13 | 9 |
| 12 × 12 ft, 8 ft walls | 384 | 14 | 9 |
| 12 × 12 ft, 8 ft walls + ceiling | 528 | 19 | 13 |
| 12 × 16 ft, 8 ft walls + ceiling | 640 | 22 | 15 |
| 20 × 20 ft, 9 ft walls + ceiling | 1120 | 39 | 26 |
Includes 10% waste and no deduction for openings.
Which drywall thickness?
- 1/2 inch: the standard for interior walls.
- 5/8 inch: ceilings with 24 inch joist spacing, and fire-rated (Type X) walls such as between a garage and the house.
- Moisture-resistant board: bathrooms and laundry rooms (use cement board behind tile in wet areas).
Frequently asked questions
How many sheets of drywall do I need for a 12x12 room?
The walls of a 12 × 12 room with 8 ft ceilings are 384 sq ft. With 10% extra that is 14 sheets of 4 × 8. Add 5 more sheets for the ceiling.
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.
Is it better to use 4x8 or 4x12 drywall?
4 × 12 sheets cover more with fewer joints, which saves taping time. 4 × 8 sheets are lighter and easier for one person to carry and hang.