How this calculator works
Enter the room's length, width and wall height, how many doors and windows it has, and your sheet size (4×8, 4×10 or 4×12 feet), and this calculator adds up the wall area (perimeter × height, minus standard door and window openings) plus the ceiling area (length × width), then works out how many sheets, screws, gallons of joint compound and feet of joint tape the job typically takes.
The sheet count already includes a 10% waste allowance for cuts, breakage and layout mismatches before rounding up to a whole sheet, which is a common estimating convention for drywall installation. Screw, joint compound and tape quantities use typical published contractor estimating rates — about 1.4 screws per square foot, 1 gallon of pre-mixed joint compound per 100 square feet for a standard finish, and 0.75 linear feet of joint tape per square foot — all of which vary with framing spacing, the number of coats, and the specific product, so treat them as a shopping-list starting point rather than an exact bill of materials.
The formula
Wall area = perimeter × height, minus a standard allowance per door (21 sq ft) and window (15 sq ft)Total area = net wall area + ceiling area (length × width); sheets = ceiling(total area ÷ sheet area × 1.10)Screws ≈ total area × 1.4; joint compound (gal) ≈ total area ÷ 100; joint tape (ft) ≈ total area × 0.75Door and window allowances (21 and 15 sq ft) match the standard openings used elsewhere on this site's paint calculator, since both trades subtract the same typical rough openings from gross wall area.
Worked example: a 12 ft × 10 ft room, 8 ft walls
- Perimeter: 2 × (12 + 10) = 44 ft. Gross wall area: 44 × 8 = 352 sq ft.
- Net wall area with 1 door and 1 window: 352 − 21 − 15 = 316 sq ft. Ceiling area: 12 × 10 = 120 sq ft. Total: 436 sq ft.
- Sheets (4×8, 32 sq ft each): 436 ÷ 32 = 13.625, × 1.10 = 14.99, rounded up to 15 sheets.
- Screws: 436 × 1.4 ≈ 611. Joint compound: 436 ÷ 100 ≈ 4.4 gallons. Joint tape: 436 × 0.75 = 327 ft.
Frequently asked questions
Should I include the ceiling in my drywall order?
This calculator always adds ceiling area (length × width) to the total, since most full-room drywall jobs finish both. If you are only replacing wall drywall and keeping an existing ceiling, subtract the ceiling area from the total yourself before ordering.
Why is the waste allowance 10%?
10% is a commonly used estimating allowance for drywall to cover cuts around outlets and corners, occasional breakage, and layout mismatches between sheet size and room dimensions. Rooms with lots of jogs, closets, or odd angles often run higher; a simple rectangular room may need less.
Do these screw, compound and tape rates match every job exactly?
No — they're typical published contractor estimating rates meant for a standard 3-coat finish on studs or joists at common spacing. Heavier textures, level-5 finishes, or non-standard framing spacing all shift the real quantities, so treat these figures as a starting shopping list and buy a little extra of the consumables, which are inexpensive relative to a second trip to the store.
Which sheet size should I choose?
4×8 sheets are the standard, easiest to handle alone and to maneuver through doorways and stairwells. Longer 4×10 or 4×12 sheets reduce the number of seams to tape and mud on tall or long walls, which can mean a better finish, but they're heavier and harder for one person to hang without a lift.
How many sheets do I need for a small 8×8 ft room with 8 ft walls and no doors or windows?
About 11 sheets of standard 4×8 drywall. The perimeter is 2 × (8 + 8) = 32 ft, so gross wall area is 32 × 8 = 256 sq ft; with no doors or windows to subtract and a 64 sq ft ceiling (8 × 8), the total is 320 sq ft. At 32 sq ft per 4×8 sheet, that's 320 ÷ 32 = 10 sheets before waste, and adding the 10% waste allowance (10 × 1.10 = 11) rounds up to 11 sheets.