Drywall Calculator
Sheets = (walls + ceiling) × 1.10 ÷ sheet area. A 12 × 12 ft room with 8 ft walls and its ceiling is 528 ft²: 19 sheets of 4 × 8 ft, 5.28 gallons of joint compound. Like CertainTeed, the calculator leaves doors and windows in the area; Georgia-Pacific takes them off, which orders a little less.
Drywall sheets to buy
19 sheets
4 × 8 ft sheets · 580.8 ft² with 10 % extra
- Drywall area
- 528 ft² (49.05 m²)
- Walls
- 384 ft² (35.67 m²)
- Ceiling
- 144 ft² (13.38 m²)
- Joint compound
- 5.28 gal (20 L): 2 cartons of 3.5 gal
- Screws
- about 494 (28 per sheet on walls, 35 on the ceiling)
Fire-rated walls and ceilings follow the screw spacing of their tested assembly, not this count.
Worked examples
A 12 × 12 ft room, 8 ft walls and the ceiling, 4 × 8 ft sheets
- Walls: 2 × (12 + 12) × 8 = 384 ft²
- Ceiling: 12 × 12 = 144 ft²; total 528 ft²
- 528 × 1.10 ÷ 32 = 18.15, so 19 sheets
- Compound: 528 × 10 ÷ 1,000 = 5.28 gal, two 3.5 gal cartons
Result: 19 sheets of 4 × 8 ft, 2 cartons of joint compound, about 494 screws.
Checked by the automated test “drywall — 12 × 12 ft room, 8 ft walls and ceiling → 528 ft², 19 sheets of 4 × 8, 5.28 gal of compound (2 cartons), 494 screws”.
Screws in one 4 × 8 ft sheet, framing 16 in apart
- Wall, sheet standing: 48 ÷ 16 + 1 = 4 studs, 96 ÷ 16 + 1 = 7 screws each: 28
- Ceiling, sheet across the joists: 96 ÷ 16 + 1 = 7 joists, 48 ÷ 12 + 1 = 5 screws each: 35
Result: About 28 screws per sheet on walls, 35 on ceilings.
Checked by the automated test “drywall — screws per 4 × 8 sheet from the USG spacing: 28 on walls, 35 on ceilings at 16 in; 21 and 25 at 24 in”.
How it works
Walls = 2 × (length + width) × height − large openings
Drywall area = walls + ceiling
Sheets = drywall area × (1 + waste %) ÷ sheet area (32, 40 or 48 ft²), rounded up
Joint compound (gal) = drywall area × 10 ÷ 1,000
Screws per sheet = framing members crossed × (sheet span ÷ screw spacing + 1)
Assumptions
- Screw spacing from USG: every 16 in on walls, every 12 in on ceilings, into wood or steel framing. Georgia-Pacific hangs wall sheets horizontally, across the studs: the count is the same either way at 16 in (28 screws per 4 × 8 ft sheet, 40 per 4 × 12) and one screw lower at 24 in, 20 instead of 21. Ceiling sheets run across the joists; the count is an estimate.
- Joint compound: USG gives about 10 gallons per 1,000 ft² of drywall for its ready-mixed all purpose compound, sold in 3.5 gallon cartons.
- 10 % waste. Fire-rated assemblies follow the fastener spacing of their own fire test, not this count.
Reference table
| Room | 4 × 8 ft, walls only | 4 × 8 ft, walls and ceiling | 4 × 12 ft, walls and ceiling |
|---|---|---|---|
| 10 × 10 ft | 11 | 15 | 10 |
| 12 × 12 ft | 14 | 19 | 13 |
| 12 × 15 ft | 15 | 22 | 15 |
| 15 × 20 ft | 20 | 30 | 20 |
No openings deducted. 4 × 12 ft sheets cut the number of joints, not the area.
Before you buy
- Sheet length. Georgia-Pacific suggests 12 ft sheets instead of 8 ft, depending on the room, to avoid end joints; check that they fit your stairs and doors.
- Screws. Use coated gypsum board screws: Georgia-Pacific warns that wood screws tear the board.
Common mistakes
- Ordering the area without waste Georgia-Pacific allows 10 to 15 % for cutting and piecing: 528 ft² of drywall takes 19 sheets of 4 × 8 ft with 10 % waste, against 17 without, and still 19 at 15 %.
- Deducting outlets and every door CertainTeed subtracts no door, window or outlet, and neither does this calculator: the openings field is for large ones such as a garage door.
- Wall screw spacing on the ceiling USG asks for a screw every 12 in on ceilings against 16 in on walls: a 4 × 8 ft ceiling sheet takes about 35 screws, not 28.
- Applying the count to a fire-rated wall USG sends rated assemblies to their fire test for fastener type and spacing: use that listing, not this estimate.
Frequently asked questions
How many screws per sheet of drywall?
About 28 on a wall and 35 on a ceiling for a 4 × 8 ft sheet on framing 16 in apart, with USG's spacing of a screw every 16 in on walls and 12 in on ceilings. On framing 24 in apart: about 21 and 25.
How much drywall do I need?
Add the walls (distance around × height) and the ceiling, then add 10 %. A 12 × 12 ft room with 8 ft walls is 528 ft² of drywall, 580.8 ft² of sheets to buy.
How many sheets of drywall do I need?
Divide the area plus 10 % by the area of one sheet, 32 ft² for 4 × 8 ft or 48 ft² for 4 × 12 ft, and round up: 580.8 ft² is 19 sheets of 4 × 8 ft or 13 of 4 × 12 ft.
How many sheets of drywall for a 12x12 room?
With 8 ft walls and 10 % waste: 14 sheets of 4 × 8 ft for the walls alone, 19 with the ceiling.
How much drywall mud do I need?
USG gives about 10 gallons of ready-mixed all purpose joint compound per 1,000 ft² of drywall: 5.28 gallons for 528 ft², two 3.5 gallon cartons.
Sources
Formula, examples and sources checked on by the Yardstick Math team. How we check our formulas.
- FAQ 1595: screw spacing for gypsum panels (12 in on ceilings, 16 in on walls) — USG, accessed
- Sheetrock all purpose joint compound, submittal sheet J1508 (coverage about 10 gal per 1,000 ft², 3.5 gal carton) — USG, accessed
- ToughRock gypsum board Wallworks guide (subtract doors and windows, allow 10 % to 15 % overage, avoid end joints) — Georgia-Pacific Gypsum, accessed
- Drywall calculator: do not subtract for doors, windows or outlets — CertainTeed, accessed