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Drywall Calculator
Enter the room size to get the sheet count, plus the mud and screws you will need — the two things everyone underestimates and has to make a second trip for.
How the drywall calculation works
- Measure the room and work out total wall area from the perimeter and ceiling height.
- Deduct 21 ft² per door and 15 ft² per window.
- Add 10 percent waste for cuts, and 15 percent if the room has many corners or you are hanging on a ceiling.
- Divide by 32 — the area of a standard 4 ft × 8 ft sheet.
- Allow about one gallon of joint compound per 300 ft² and 1.1 screws per ft².
The formula
Wall area = 2 × (Length + Width) × Height, minus 21 ft² per door and 15 ft² per window. Sheets = area × (1 + waste) ÷ 32.
Buying materials?
Compare prices before you order:
- Drywall sheets paste your link here
- Joint compound paste your link here
- Drywall screws paste your link here
Common questions
What size are standard drywall sheets?
The common sheet is 4 ft × 8 ft, which is 32 ft². You can also buy 4 × 12 sheets, which cut waste in rooms with 9 or 10 ft ceilings but are heavy and awkward to handle alone.
How much waste should I add?
Ten percent for a simple room. Go to 15 percent for rooms with lots of corners, windows or unusual shapes, and if you are also doing the ceiling.
How much joint compound do I need?
Roughly one gallon per 300 ft² of board for a level 4 finish. A proper level 5 finish or heavy texture takes noticeably more.
How many screws per sheet?
About 32 screws for a 4 × 8 sheet on studs at 16 inches on centre, so roughly one per square foot. This calculator allows 1.1 per ft² to cover waste.
Should drywall be hung horizontally or vertically?
Horizontally, across the studs. It means fewer joints, and joints fall at a height where they are easy to tape. Vertical hanging is faster but leaves more seams to finish.