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How to Calculate Drywall
Drywall (also called sheetrock or gypsum board) comes in sheets. Knowing the total area lets you figure out how many sheets to buy, plus the tape, compound, and screws you'll need.
Basic Formula
Step by Step
- Calculate wall area: Perimeter × wall height
- Add ceiling if applicable: Length × width
- Subtract openings: Doors (~21 sq ft), windows (~15 sq ft)
- Add waste factor: 10–20% extra for cuts and scrap
- Divide by sheet size: 32, 40, or 48 sq ft per sheet
Supply Estimates
- Joint compound: ~1 gallon per 100 sq ft (3 coats: tape coat, fill coat, finish coat)
- Drywall tape: 1 roll (250 ft) per 300–375 sq ft
- Drywall screws: ~32 screws per 4×8 sheet (every 12" on edges, 16" in field)
Choosing the Right Drywall
- Regular (½"): Standard for walls and ceilings with 16" stud spacing
- Lightweight (½"): 25% lighter — easier to handle, same applications
- ⅝" Drywall: Required for ceilings with 24" joist spacing; adds fire resistance
- Moisture-Resistant (Green Board): For bathrooms, kitchens, and laundry rooms
- Fire-Rated (Type X): Required for garage walls/ceilings attached to living spaces
Which Sheet Size?
- 4 × 8 ft: Most common, easiest to handle for DIY
- 4 × 10 ft: Fewer seams for 9–10 ft walls
- 4 × 12 ft: Fewer seams for large walls, but heavy and harder to maneuver
Frequently Asked Questions
What size drywall should I use?
Use ½" drywall for most walls and ceilings with standard 16" stud spacing. Use ⅝" for ceilings with 24" joist spacing or where fire rating is required (like garage-to-house walls).
How much joint compound do I need?
Plan for about 1 gallon of pre-mixed joint compound per 100 square feet of drywall. You'll apply three coats: a tape coat, a fill coat, and a finish coat. A 4.5-gallon bucket covers roughly 450 sq ft.
Can I hang drywall by myself?
Walls are manageable solo with a drywall lift or prop. Ceilings are much harder alone — a drywall lift (rental ~$40/day) is strongly recommended for ceiling sheets.
How many screws per sheet of drywall?
About 32 screws per 4×8 sheet. Place screws every 12 inches along edges and every 16 inches in the field (center of the sheet). Keep screws at least ⅜" from edges to prevent crumbling.