How to use it
- Enter the room's length, width and wall height. Add inches if you have them, so 8 ft 1 in is 8 and 1.
- Pick walls and ceiling, or walls only.
- Count the doors and windows and check the size of each. The door default is a standard 3 ft × 6 ft 8 in door.
- Choose how to treat openings, the sheet size and the waste factor.
- Count the outside corners if you want corner bead figured.
- Type your prices in the cost section to price the job.
Results update as you type. Copy result gives you a plain-text material list, and the page address saves your numbers so you can bookmark the room.
The formula
Wall area = 2 × (Length + Width) × Wall height
Ceiling area = Length × Width
Net area = Wall area − Openings you deduct + Ceiling area
Sheets = Area × (1 + Waste % ÷ 100) ÷ Sheet area, rounded up
Compound, tape and screws = Net area × rate per 1,000 sq ft
Corner bead = Outside corners × (Wall height ÷ Bead length, rounded up)
A 4 × 8 sheet covers 32 sq ft, a 4 × 10 covers 40 and a 4 × 12 covers 48. Walls and ceiling are rounded up separately, because they're often different board.
Worked example: a 12 ft × 14 ft bedroom with 8 ft walls
- Walls: 2 × (12 + 14) × 8 = 416 sq ft. Ceiling: 12 × 14 = 168 sq ft
- One door (20 sq ft) and two windows (15 sq ft each) take out 50 sq ft, leaving 366 sq ft of wall and 534 sq ft in all
- Wall sheets: 366 × 1.10 = 402.6 ÷ 32 = 12.58, so 13 of 4 × 8
- Ceiling sheets: 168 × 1.10 = 184.8 ÷ 32 = 5.78, so 6. That's 19 sheets, or 608 sq ft of board
- Compound: 534 × 9 ÷ 1,000 = 4.81 gal, so 2 buckets of 4.5 gal
- Tape: 534 × 370 ÷ 1,000 = 197.58 ft (about 198), so 1 roll of 500 ft
- Screws: about 534, or 3 lb at 240 per pound. Two outside corners take 2 pieces of 8 ft bead
Deduct the door only and the count goes to 20 sheets. Deduct nothing and it's 21.
Should you deduct doors and windows?
Most of a sheet hung over a window still gets bought. The piece you cut out is usually too small or oddly shaped to use anywhere else, so it goes in the trash. That's why many estimators don't deduct small openings at all and only take out the big ones, like doors, patio doors and wide cased openings. In a room with several windows, “Deduct doors only” is the safer count. “Don't deduct openings” is the most conservative and suits rooms that are cut up with soffits, angles or niches.
When 12 ft sheets make sense
Longer sheets mean fewer butt joints, the end-to-end seams that are the hardest to finish flat. On a 12 ft wall, one 12 ft sheet per row has no butt joint at all. The trade-off is weight and handling: a 4 × 12 sheet of 1/2 in board takes two people, and it has to fit through the door, up the stairs and around the corners to get to the room. For small rooms, closets and tight access, 4 × 8 sheets are easier.
Ceiling board vs. wall board
Ceilings hold the board upside down, and wet texture or mud adds weight, so standard 1/2 in board can sag between joists. Board makers sell 1/2 in sag-resistant ceiling board for this, and many crews use 5/8 in. Check the board maker's span table and your local code for your framing spacing. For bathrooms and other damp areas, moisture-resistant board is a common choice. Your local code decides what's required behind tile and in tub and shower areas.
Common mistakes
- Forgetting the ceiling. In a 12 × 14 room the ceiling is 168 sq ft, six more sheets with waste.
- Using too little waste. Every corner, outlet and window creates scrap. Running short means a second trip and sometimes a mismatched board.
- Measuring to the trim. Measure the framing or the old wall, floor to ceiling, not the baseboard.
- Missing window returns. If windows get drywall returns instead of jambs, add board and corner bead for those strips.
Questions people ask
How many sheets of drywall do I need for a 12 × 12 room?
With 8 ft walls, one door and no windows deducted, the walls are 364 sq ft net. With 10% waste that's 13 sheets of 4 × 8. The ceiling adds 5 more, for 18. Enter your own room above for an exact count.
Should I hang drywall sideways?
On walls, most hangers run sheets horizontally. It puts the long tapered edge across the studs, bridges uneven framing and usually means fewer feet of seam to finish. The sheet count here works either way, because it's based on area.
How much joint compound do I need?
USG's guidance is about two 4.5 gal pails of ready-mixed all purpose compound per 1,000 sq ft of board. A heavy texture or a smooth, high-level finish takes more. Change the rate if your finisher uses a different number.
Why is one screw per square foot the default?
Screws are usually placed about 12 in apart on ceilings and 16 in apart on walls, the common maximums for wood framing. That works out to roughly one per square foot. Follow the spacing your code and board maker call for.
How do I figure the cost?
Type the price per sheet, bucket, roll, pound and piece of bead in the cost section, plus tax and any labor. Prices vary a lot by area and change often, so check your store or supplier.