Drywall Calculator
Sheets, screws, joint compound and tape for a room, working from wall area with the openings taken off and the ceiling optional.
Drywall needed
19sheets
- Area to cover
- 594 sq ft
- 4x8 sheets
- 19
- 4x9 sheets
- 17
- 4x10 sheets
- 15
- 4x12 sheets
- 13
- Screws
- 700
- Joint compound
- 6 gallons
- Joint tape
- 238 ft
- Includes the ceiling. Ceilings take more screws than walls and are far easier with a second person or a panel lift.
- Screws, compound and tape are trade rules of thumb — about 32 screws a sheet, a gallon of compound per 100 square feet, and 400 feet of tape per 1,000. Treat them as a shopping list, not a precise take-off.
- Longer sheets cost more but leave fewer butt joints to tape, which is usually the slowest part of the job.
About the drywall calculator
Wall area is the room's perimeter times its height, the same starting point as painting. If you are boarding the ceiling too, that is the floor area added on, since a ceiling is the same size as the floor beneath it.
Sheet size is worth thinking about rather than defaulting to 4x8. Longer sheets cost more each but leave fewer butt joints, and taping a butt joint flat is the slowest and most skilled part of the whole job. That is why professionals reach for twelve-footers wherever the room allows.
The screw, compound and tape figures are trade rules of thumb — about 32 screws a sheet, a gallon of compound per hundred square feet, and 400 feet of tape per thousand. Treat them as a shopping list rather than a precise take-off.
What it works out
- Sheets in 4x8, 4x9, 4x10 and 4x12
- Screws, joint compound and tape
- Walls only, or walls plus the ceiling
The formula
Sheets = ((Wall area + Ceiling − Openings) × (1 + Waste)) ÷ Sheet area
Wall area is the room's perimeter multiplied by its height, the same starting point as painting. If you are boarding the ceiling too, add the floor area — length times width — since a ceiling is the same size as the floor beneath it.
Doors and windows come off next, then a waste allowance goes on. Ten per cent is normal: drywall is cut to fit around openings and at corners, and the offcuts are rarely the right shape for anywhere else.
Divide by the area of one sheet and round up. A 4x8 sheet is 32 square feet, 4x10 is 40 and 4x12 is 48. Longer sheets cost more per sheet but leave fewer butt joints, and taping butt joints flat is the slowest and most skilled part of the whole job — which is why professionals reach for 12-footers wherever the room allows.
- Wall area
- Perimeter times ceiling height.
- Ceiling
- Length times width, added only if you are boarding overhead.
- Openings
- Doors at 36 by 80 inches and windows at 3 by 4 feet.
- Sheet area
- 32 square feet for a 4x8, 40 for a 4x10, 48 for a 4x12.
A worked example
A fourteen by twelve room with eight-foot ceilings, ceiling included, in 4x8 sheets.
That works out to 19 sheets.
- Area to cover
- 594 sq ft
- 4x8 sheets
- 19
- 4x9 sheets
- 17
- 4x10 sheets
- 15
- 4x12 sheets
- 13
- Screws
- 700
- Joint compound
- 6 gallons
- Joint tape
- 238 ft
Questions
How many sheets of drywall do I need for a 12x12 room?
With eight-foot ceilings and the ceiling boarded, that is about 384 square feet of wall plus 144 of ceiling. Less a door and two windows and plus ten per cent waste, it comes to roughly 17 sheets of 4x8.
Should I use 4x8 or 4x12 sheets?
Use the longest sheet the room and your access allow. Fewer sheets means fewer butt joints, and butt joints are the hardest thing to hide in a finished wall. The trade-off is weight — a 4x12 half-inch sheet is over 80 pounds and awkward for one person.
How many screws per sheet of drywall?
About 32 for a wall sheet on 16-inch centres, and more for a ceiling where the board is fighting gravity. Buying by the pound, a five-pound box holds roughly 500 screws of the usual length.
How much joint compound do I need?
Roughly one gallon per 100 square feet of drywall for taping and three coats of finishing. A pre-mixed bucket holds about 4.5 gallons, so it covers around 450 square feet.
Should I subtract doors and windows?
Subtract them, but keep the waste allowance on the full area. Openings create offcuts rather than saving board, because the pieces cut out are rarely usable elsewhere.
What thickness of drywall should I use?
Half-inch is standard for walls and ceilings in a home. Five-eighths is used where fire rating or sound resistance is required, and is stiffer over joists at wider spacing. Check local building rules, which often specify it for garages and ceilings.