Drywall Calculator
Estimate drywall sheets, screws, joint compound and tape for a room from its size, doors and windows.
How many sheets of drywall do I need?
Sheets = (Wall area − openings + ceiling area) × (1 + waste) ÷ sheet area
A 12 × 12 ft room with 8 ft walls has 2 × (12 + 12) × 8 = 384 ft² of wall. Subtract one door (21 ft²) and two windows (30 ft²) to get 333 ft², add the 144 ft² ceiling for 477 ft², and add 10% waste: 17 sheets of 4 × 8.
Which sheet size to use
4 × 8 sheets are the easiest to carry and fit in most vehicles. 4 × 12 sheets cover a 12 ft wall in one piece, which means fewer butt joints to tape and a smoother finish, but they weigh around 70–80 lb at 1/2 in thickness and usually need two people. Ceilings are often hung with 5/8 in or "ceiling" board that resists sagging.
Fasteners, mud and tape
| Material | Rule of thumb |
|---|---|
| Drywall screws | About 1 per ft² (roughly 32 per 4 × 8 sheet with framing 16 in on center) |
| Joint compound (ready-mixed) | About 9–10 gallons per 1,000 ft² for taping and two finish coats |
| Paper joint tape | About 370 ft per 1,000 ft² |
These are estimates for standard Level 4 finishing. A Level 5 skim coat, many inside corners or patch work will use more compound.
Frequently asked questions
How many sheets of drywall for a 12×12 room?
About 13 sheets of 4×8 for the walls alone, or 17 including the ceiling, with 10% waste and one door and two windows deducted.
Should I deduct windows and doors?
Yes for estimating, but many pros deduct only half of each opening because cut-offs around them are rarely usable.
What thickness of drywall should I use?
1/2 in is standard for walls; 5/8 in is used for ceilings, fire-rated walls and better sound control.
Last reviewed October 2026. Results are estimates; check important decisions with a qualified professional.