Wall Area: Net square footage of wall surface after subtracting standard openings — this is how much drywall you actually need to cover.
Drywall Sheets (4×8): Number of standard 4-by-8-foot sheets. Each sheet covers 32 square feet. The count always rounds up since you can't buy partial sheets.
Joint Compound: Gallons of pre-mixed mud needed for taping and finishing all joints and fastener holes, at roughly 1.5 gallons per 100 square feet.
Drywall Tape: Linear feet of paper or mesh tape for seams, estimated at about 300 feet per 1,000 square feet of drywall.
How This Calculator Works
You enter the room's length, width, and ceiling height, plus the number of doors and windows. The tool calculates the perimeter, multiplies by ceiling height for gross wall area, then subtracts 21 square feet per door and 15 square feet per window. It divides the net area by 32 for sheets, and applies standard ratios for compound and tape.
Quick Questions
Why does it deduct 21 sq ft per door?
A standard interior door opening is about 3 feet wide by 7 feet tall (21 sq ft). If your doors are significantly larger, adjust the count.
Should I buy extra sheets?
Yes. Buy 10–15% more than the calculator shows to cover cutting waste, damaged sheets, and mistakes during installation.
Can I use this for ceilings too?
This version calculates walls only. For ceilings, add the room's length × width to the sheet count separately.
What about 4×12 sheets?
Some professionals use 4×12 sheets (48 sq ft each) to reduce seams. Divide the net area by 48 instead of 32 for that sheet size.
How much compound do I really need?
The 1.5 gal per 100 sq ft estimate covers three coats of finishing. Skim-coating entire walls requires significantly more.
Sources
Gypsum Association (drywall specifications, installation guidelines, fire ratings)