Drywall Calculator
Calculate drywall sheets, joint compound, tape, and screws needed for your room. See also Paint Calculator, Flooring Calculator, and Insulation Calculator.
How to Use the Drywall Calculator
Measure your room's length, width, and ceiling height in feet. Enter the number of standard doors (approximately 21 sq ft each) and windows (approximately 15 sq ft each) to subtract from the total wall area. The calculator adds 10% waste factor to account for cuts, damaged pieces, and fitting around obstacles. Results include the number of standard 4x8 and 4x12 sheets needed, plus joint compound, tape, and screw quantities for a complete installation.
Formula
Wall Area = Perimeter x Height - (Doors x 21) - (Windows x 15)
Ceiling Area = Length x Width
Sheets (4x8) = Total Area x 1.10 / 32 sq ft per sheet
Joint Compound = 0.5 gallons per 100 sq ft
Screws = 1.5 per sq ft (every 12" on edges, 16" in field)
Example Calculation
Room: 12 ft x 10 ft, 8 ft ceiling, 1 door, 2 windows
Perimeter = 2 x (12 + 10) = 44 ft
Gross wall area = 44 x 8 = 352 sq ft
Net wall area = 352 - 21 - 30 = 301 sq ft
Ceiling = 12 x 10 = 120 sq ft
Total = 421 sq ft x 1.10 = 463 sq ft
4x8 sheets = 463 / 32 = 15 sheets
Reference Table
| Sheet Size | Area (sq ft) | Thickness | Weight | Common Use |
|---|---|---|---|---|
| 4 x 8 ft | 32 | 1/2 in | 57 lbs | Standard walls |
| 4 x 10 ft | 40 | 1/2 in | 71 lbs | 9-10 ft ceilings |
| 4 x 12 ft | 48 | 1/2 in | 85 lbs | Tall walls, fewer joints |
| 4 x 8 ft | 32 | 5/8 in | 70 lbs | Ceilings, fire-rated |
| 4 x 8 ft | 32 | 1/4 in | 38 lbs | Curved surfaces |
Frequently Asked Questions
How many sheets of drywall do I need for a 12x12 room?
A 12x12 room with 8-foot ceilings needs approximately 18 sheets of 4x8 drywall for walls and ceiling combined (including 10% waste). Walls alone require about 14 sheets, and the ceiling adds 4-5 more sheets.
What thickness drywall should I use?
Use 1/2-inch drywall for standard walls with studs 16 inches on center. Use 5/8-inch for ceilings (to prevent sagging), fire-rated walls, and soundproofing applications. Use 1/4-inch only for curved surfaces or as a lamination layer.
How much joint compound do I need?
Plan for approximately 0.5 gallons of joint compound per 100 square feet of drywall. A standard 4.5-gallon bucket covers about 900 square feet for three coats of finishing. Pre-mixed compound is easier for beginners.
Should I hang drywall horizontally or vertically?
Hang drywall horizontally on walls — this creates fewer joints, places the tapered edges at a convenient working height, and adds structural strength across studs. Ceilings should be hung perpendicular to joists.
How many screws per sheet of drywall?
Use approximately 28-32 screws per 4x8 sheet. Place screws every 12 inches along edges and every 16 inches in the field (center of the sheet). Keep screws at least 3/8 inch from edges to prevent crumbling.
What is the waste factor for drywall?
A 10% waste factor is standard for rectangular rooms. For rooms with many corners, angles, or cutouts (like bathrooms), use 12-15%. Complex layouts with cathedral ceilings or multiple soffits may need 15-20% extra material.