A 14 by 12 foot room with 8 foot walls, one door and two windows needs 13 sheets of 4 × 12 ft drywall for the walls and ceiling, with 10% waste: 9 for the walls and 4 for the ceiling. Hung on studs and joists 16 inches apart, that is about 560 screws, 5.4 gallons of all purpose joint compound and 200 feet of paper tape.
How the drywall calculator works
Drywall is bought by the sheet, so the calculator turns every surface into square feet, adds the waste allowance and divides by the area of one sheet. Walls and ceilings are rounded up separately, because a ceiling sheet is hung and cut on its own.
Sheets = (perimeter × wall height − doors − windows) × (1 + waste) ÷ sheet area, plus ceiling length × width × (1 + waste) ÷ sheet area
A 4 × 8 sheet covers 32 sq ft, a 4 × 10 covers 40 and a 4 × 12 covers 48. Each door takes off 3 ft × 6 ft 8 in (20 sq ft) and each window 3 × 4 ft (12 sq ft).
Worked example: walls and ceiling of one room
The default room is 14 × 12 ft with 8 ft walls:
- Perimeter 2 × (14 + 12) = 52 ft, walls 52 × 8 = 416 sq ft
- Minus one door (20 sq ft) and two windows (24 sq ft): 372 sq ft of wall
- Ceiling 14 × 12 = 168 sq ft
- Walls: 372 × 1.1 ÷ 48 = 8.5, so 9 sheets; ceiling: 168 × 1.1 ÷ 48 = 3.9, so 4 sheets
With 4 × 8 sheets the same room takes 13 for the walls and 6 for the ceiling, 19 in all. Longer sheets mean fewer butt joints to tape, but a 4 × 12 sheet of ½ in board is a two person lift and may not turn up a staircase.
Drywall for walls, for ceilings or the whole house
Switch "What gets drywall" to walls only or ceiling only, and the sheet count, screws and mud follow. For a whole house, add a room for each space, or set "Rooms like this" for identical bedrooms. Adding a 12 × 10 ft room with one door and one window to the example brings the job to 692 sq ft of wall and 288 sq ft of ceiling: 16 wall sheets and 7 ceiling sheets of 4 × 12. If you already know the square footage, measure by square footage instead and type the wall and ceiling areas; the room square footage calculator works them out for odd shapes.
How many screws per sheet of drywall
The Gypsum Association's application standard GA-216 sets the maximum screw spacing on wood framing: 12 in on ceilings and 16 in on walls when the framing is 16 in on center, and 12 in on both when it is 24 in on center. The calculator places a row of screws on every stud or joist a sheet crosses, both ends included, so a sheet hung across the framing gets:
| Sheet | Walls, 16 in o.c. | Ceilings, 16 in o.c. | Walls or ceilings, 24 in o.c. |
|---|---|---|---|
| 4 × 8 ft | 7 studs × 4 = 28 | 7 joists × 5 = 35 | 5 × 5 = 25 |
| 4 × 10 ft | 8 × 4 = 32 | 8 × 5 = 40 | 6 × 5 = 30 |
| 4 × 12 ft | 10 × 4 = 40 | 10 × 5 = 50 | 7 × 5 = 35 |
That works out to about 875 to 1,040 screws per 1,000 sq ft, close to the "approx. 1,000 Type W screws" per 1,000 sq ft that USG's Gypsum Construction Handbook gives for walls at 16 in. USG's screw selector lists 1¼ in Type W coarse thread screws for single-layer ½ and ⅝ in board on wood studs; GA-216 asks for at least ⅝ in of penetration into the framing. Screws stay at least ⅜ in from the paper edges.
Which thickness and sheet size
½ in board is the usual choice for walls. For ceilings on joists 24 in apart, GA-216 calls for ⅝ in board hung across the joists USG's ⅝ in Firecode X is the fire-rated version. GA-216 does not allow ¼ in board on its own; it is made for laminating over old plaster, so pick it only for that.
USG lists panel lengths from 8 to 16 ft. The calculator offers 8, 10 and 12 ft, the lengths home centers stock.
Mud, tape and corner bead
The joint compound and tape come from USG's published coverage: about 10 gallons of Sheetrock All Purpose (9.4 gallons of the lightweight Plus 3) and 370 feet of paper tape per 1,000 sq ft of board, for the usual three coats. The example's 540 sq ft takes 5.4 gallons, two 4.5 gallon pails, and 200 ft of tape, one 250 ft roll. For finish levels, bags of setting compound and a Level 5 skim coat, use the drywall mud calculator.
Corner bead covers outside corners only: soffit edges, wall ends, window returns. Enter how many there are and each gets a full-height piece; USG sells Dur-A-Bead in 8, 9, 10 and 12 ft lengths, so a corner taller than one piece takes two.
Next steps
Price the job with the drywall installation cost calculator, then work out primer and paint with the paint calculator. If the walls are open, insulate first: the insulation calculator gives the R-value for your climate zone. Framing a new wall? Count studs and plates with the stud calculator. More tools for this room are in drywall, paint and walls.