How to calculate drywall
Drywall is estimated by area. Add up the surface you are covering and divide by the size of one sheet:
Sheets = total area × (1 + waste %) ÷ sheet coverage
Wall area is the room perimeter times the wall height: 2 × (length + width) × height. Tick "Include the ceiling" to add the floor-sized area overhead. Most DIYers don't subtract small openings — that buffer covers waste.
Drywall sheet sizes
| Sheet size | Coverage | Best for |
|---|---|---|
| 4 × 8 ft | 32 sq ft | Easiest to handle; most rooms |
| 4 × 10 ft | 40 sq ft | Taller walls, fewer seams |
| 4 × 12 ft | 48 sq ft | Large walls and ceilings |
Which type of drywall?
Standard white-board is fine for most walls and ceilings, but some rooms need a specialty panel:
- Standard (½ in). The default for walls; ⅜ in for curved work and ⅝ in for ceilings and where sag resistance matters.
- Moisture-resistant ("green board"). For damp areas like bathrooms — but not directly behind tile in a shower.
- Mold-resistant ("purple"). Paperless or treated board for high-humidity rooms and basements.
- Cement board. The waterproof backer for tile in showers and tub surrounds — not really drywall, but it goes in the same place.
- Type X (⅝ in fire-rated). Required between a garage and living space, and on many ceilings by code.
- Soundproof. Dense, laminated panels for media rooms and shared walls.
The finishing materials add up
- Screws: about one per square foot (≈32 per 4×8 sheet) at 16-inch framing spacing.
- Joint compound & tape: needed for every seam and screw head — size the mud with our joint compound calculator.
- Corner bead: measure each outside corner separately.
- Primer: a coat of drywall primer (PVA) evens out the porous paper and joint compound before painting.
How much does drywall cost?
Sheets run about $12–$20 each, so the board for an average room is modest — the real cost of a drywall job is the labor to hang, tape, and finish it, which typically runs $1.50–$3.50 per square foot installed.
Hanging and finishing drywall
- Hang the ceiling first, then the walls, so the wall panels help support the ceiling edges.
- Run panels horizontally on walls, screwing into every stud about every 12–16 inches and keeping screws just dimpled below the surface, not breaking the paper.
- Tape the seams. Embed paper or mesh tape in a first coat of joint compound over every seam and inside corner, and add corner bead on outside corners.
- Three coats of mud. Follow with two wider finish coats, feathering the edges, and let each dry before the next.
- Sand and prime. Sand smooth, then roll on a coat of drywall primer (PVA) before painting.