Drywall Calculator
Enter the room size to find the wall and ceiling area and the number of drywall sheets to buy. Doors and windows are subtracted at standard sizes.
Result
- Wall area
- 384 sq ft
- Ceiling area
- 144 sq ft
- Net area to cover
- 492 sq ft
- Area with waste
- 541.2 sq ft
Formula
- Wall area = 2 × (length + width) × height
- Ceiling area = length × width
- Net area = walls + ceiling − doors × 21 − windows × 15
- Sheets = net area × (1 + waste) ÷ sheet area, rounded up
How the Drywall Calculator works
Drywall is estimated by surface area. Add the four walls and the ceiling, subtract large openings, add waste for cuts, and divide by the area of one sheet.
A standard interior door opening is about 3 ft × 7 ft, or 21 square feet. A typical window is about 3 ft × 5 ft, or 15 square feet. Many installers skip the subtraction for small openings because the offcuts are rarely reusable.
Worked example
A 12 ft × 12 ft room with 8 ft walls has 2 × 24 × 8 = 384 sq ft of wall and 144 sq ft of ceiling. Subtracting one door and one window leaves 492 sq ft. With 10 percent waste that is 541.2 sq ft, or 541.2 ÷ 32 = 16.9, so 17 sheets of 4 × 8.
Frequently asked questions
How many sheets of drywall do I need for a 12 × 12 room?
About 17 sheets of 4 × 8 for the walls and ceiling of a room with 8 foot walls, one door and one window, including 10 percent waste. Walls alone need about 12 sheets.
Is sheetrock the same as drywall?
Yes. Sheetrock is a brand name for drywall, which is also called gypsum board or plasterboard.
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