Drywall Calculator
Work out exactly how many sheets of drywall you need for a room, plus the screws, joint compound and tape that go with it. Add your own prices for a full cost estimate.
How this calculator works
The calculator totals your wall and ceiling area, subtracts openings, divides by sheet size, and adds a waste allowance for cuts around corners and fixtures:
sheets = ceil( area ÷ sheet coverage × (1 + waste%) )
Screws, joint compound and tape are then estimated from standard rules of thumb — 32 screws per sheet, roughly 1 gallon of compound per 100 sq ft across all coats, and a rough tape length based on typical seam density. Treat these three as a starting shopping list, not an exact count, since actual seam layout varies by room.
Worked example
A 12 ft × 10 ft room, 8 ft ceilings, one door, using 4×8 sheets:
- Wall area: (12 + 10) × 2 × 8 = 352 sq ft, minus a 21 sq ft door = 331 sq ft.
- Each 4×8 sheet covers 32 sq ft: 331 ÷ 32 ≈ 10.34 sheets before waste.
- Add 10% waste and round up: 10.34 × 1.10 ≈ 11.4 → buy 12 sheets.
- Screws: 12 × 32 = 384 screws. Compound: 331 ÷ 100 ≈ 4 gallons.
Choosing sheet thickness
| Thickness | Typical use | Why |
|---|---|---|
| 3/8" | Repairs, curved walls | Flexible enough to bend around curves |
| 1/2" | Standard walls & ceilings | Good balance of cost, weight and rigidity |
| 5/8" | Ceilings, garage walls | Resists sagging over wider spans; often fire-rated |
Many local codes require fire-rated (Type X) 5/8" drywall on walls and ceilings shared between an attached garage and living space — check your local code before buying standard sheets for that job.
Frequently asked questions
Should I use ½ inch or ⅝ inch drywall?
½ inch is the standard choice for most interior walls and ceilings with framing on 16 inch centers. ⅝ inch is thicker and more resistant to sagging, so it's common on ceilings with wider joist spacing, and often required by code for garage walls shared with living space because of its better fire resistance.
How many screws does a sheet of drywall need?
A standard 4×8 sheet typically takes around 32 screws, spaced roughly every 16 inches along each framing member the sheet crosses. Ceilings and sheets on 24 inch framing can need a few more to avoid sagging between supports.
How much joint compound do I need for an average room?
A rough rule of thumb is about 1 gallon per 100 square feet of drywall, covering the typical three coats (embedding, filling and finishing) combined. Textured finishes or a large number of butt joints can push this higher.
Is fire-rated drywall required for a garage?
Many building codes require fire-rated (Type X) drywall on walls and ceilings shared between an attached garage and living space, since it slows the spread of fire. Requirements vary by location, so check your local building code before buying standard drywall for a garage conversion.