How This Calculator Works
The calculator computes the perimeter of your room (2 x length + 2 x width), multiplies by ceiling height to get total wall area, then subtracts standard openings: 21 square feet per door (3 x 7 ft) and 15 square feet per window (3 x 5 ft). If you include the ceiling, it adds length x width. A 10% waste factor covers cuts, odd angles, and mistakes.
Drywall Sheet Sizes
| Sheet Size | Area (sq ft) | Weight | Best For |
|---|---|---|---|
| 4 x 8 ft | 32 | ~50 lbs (1/2") | Standard rooms, DIY projects |
| 4 x 12 ft | 48 | ~77 lbs (1/2") | Fewer joints, pro installations |
| 4 x 10 ft | 40 | ~63 lbs (1/2") | 9-10 ft ceilings |
| 54" x 8 ft (4.5 x 8) | 36 | ~56 lbs (1/2") | 8 ft walls with one horizontal joint |
Drywall Thickness Guide
| Thickness | Application | Cost per Sheet (4x8) |
|---|---|---|
| 1/4" | Curved walls, layering over existing drywall | $10-14 |
| 3/8" | Repair patches, covering old plaster | $11-15 |
| 1/2" | Standard walls and ceilings (most common) | $12-18 |
| 5/8" | Fire-rated walls, ceilings with 24" joist spacing, soundproofing | $14-22 |
Materials Checklist
Beyond drywall sheets, a typical room needs these supplies. The calculator covers the top items, but corner bead and sanding supplies depend on your room layout.
- Joint compound (mud) — about 12.5 lbs per 100 sq ft of drywall. A 20 lb box covers about 160 sq ft.
- Paper tape — one 75 ft roll covers about 300 sq ft. Mesh tape is easier for beginners but paper tape is stronger.
- Drywall screws— coarse thread, 1-1/4" for 1/2" drywall. About 32 screws per 4x8 sheet, spaced 12" apart on studs.
- Corner bead — metal or paper-faced, one 8 ft piece per outside corner.
- Sandpaper — 120 grit for first pass, 150 grit for finish. A sanding pole speeds up the work.
FAQ
How many sheets of drywall for a 12x12 room?
A 12x12 room with 8 ft ceilings has 384 sq ft of wall area. Subtract one door (21 sq ft) and two windows (30 sq ft) for 333 sq ft. With 10% waste, that is about 366 sq ft, or 12 standard 4x8 sheets. Including the ceiling adds another 5 sheets, for 17 total.
Should I use 4x8 or 4x12 drywall sheets?
For 8-ft ceilings, 4x8 sheets hung horizontally means one seam at 4 ft. Using 4x12 sheets reduces the number of vertical seams since each sheet covers 12 linear feet. Pros prefer 4x12 for fewer joints, but they are heavy (77 lbs) and harder to handle alone.
How much does it cost to drywall a room?
Materials for a 12x12 room (walls only) cost roughly $150-250: $12-18 per sheet x 12 sheets plus mud, tape, screws, and corner bead. Professional installation runs $1.50-3.00 per square foot, putting a full-room job at $500-1,000 for labor.
Do I need 5/8 drywall for the ceiling?
If ceiling joists are spaced 24 inches apart, yes — 1/2" drywall sags between joists over time. With 16-inch joist spacing, 1/2" is fine. Building codes in many areas also require 5/8" fire-rated (Type X) drywall on ceilings in attached garages and between floors in multi-story homes.
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