How it works
Enter the room dimensions and the calculator finds the wall area (less doors and windows), adds the ceiling if you want it, and divides by the sheet size with a waste allowance.
Finishing estimates follow common manufacturer figures for a taped, three-coat finish: about 9.4 gallons of ready-mixed all-purpose compound (roughly 138 lb) and 370 feet of tape per 1,000 sq ft of board. Screws assume about one per square foot, which matches 16 in framing spacing.
Longer sheets mean fewer butt joints to finish. If you can get 12 ft sheets into the room, they often save taping time on long walls.
Formula
Sheets = [2 × (L + W) × H − openings + ceiling] × (1 + waste) ÷ sheet area. Compound ≈ 9.4 gal and tape ≈ 370 ft per 1,000 sq ft.
Questions people ask
How many sheets of drywall for a 12 × 12 room?
With 8 ft walls the walls are 384 sq ft and the ceiling 144 sq ft. After one door and one window and 10% waste that is about 17 sheets of 4 × 8.
Should I subtract windows and doors?
Subtracting them gives a tighter number, but many pros skip it for small openings because the offcuts are rarely usable. The waste factor covers the difference.
What thickness of drywall should I use?
1/2 in for most walls, and 5/8 in for ceilings with 24 in joist spacing. Under the IRC, walls between an attached garage and the house need at least 1/2 in gypsum board on the garage side; 5/8 in Type X is required on a garage ceiling with living space above.
How much joint compound do I need?
Roughly one 4.5 gallon bucket per 450 to 500 sq ft of board for a three-coat finish. Heavy texture or skim coats use much more.