How to Estimate Drywall
Drywall estimation starts with wall area: multiply the perimeter of the room by the ceiling height, then subtract openings (about 21 sq ft per standard door, 15 sq ft per window). Add the ceiling area if you're drywalling it. Divide the total by the sheet size — 32 sq ft for 4×8 sheets — and add 10% for waste from cuts and fitting.
Subtract: Doors × 21 sq ft, Windows × 15 sq ft
Sheets = (Total area × 1.10) ÷ Sheet area
Sheet Sizes: When to Use What
4×8 sheets are the standard — easiest to handle, fit through doorways, work for 8-foot walls. 4×12 sheets are preferred for ceilings and 9-foot walls because they span the full length with fewer joints. Fewer joints means less taping, less mud, and a smoother finish. 4×10 sheets split the difference and work well for 10-foot ceilings.
Joint Compound: How Much Do You Need?
Plan on about 1 gallon of premixed all-purpose joint compound per 100 sq ft of drywall — that covers three coats (taping coat, fill coat, finish coat). A 5-gallon bucket handles about 500 sq ft, which is roughly a standard bedroom. For a whole house, buy in bulk — a case of 5-gallon buckets. You'll also need roughly 375 feet of paper joint tape per 500 sq ft of drywall.