Drywall calculator: sheets, mud, tape and screws

Wall area is the room’s perimeter times its wall height; ceiling area is length times width. Openings come off if you choose to deduct them, waste is added, and each surface is divided by the area of the sheet you hang there — 32 sq ft for a 4 × 8, 40 for a 4 × 10, 48 for a 4 × 12, 54 for a 54-inch × 12 — and rounded up to whole sheets. Walls and ceilings round separately because you cannot hang a ceiling offcut on a wall of a different sheet size.

No openings deducted. Rooms with 9- or 10-foot walls usually hang 54-inch or 4 × 10 board to avoid a strip at the top.

Butt joints — where two factory-cut ends meet without a taper — are the hardest seams to finish flat, and on a ceiling every one of them shows under raking light. Twelve-foot sheets span most rooms with fewer butt joints than eights. They are heavier and usually need a drywall lift or two people, which is labor you should see in the estimate rather than discover on site.

The finishing numbers use typical consumption per 1,000 sq ft of board for a level 4 finish: about 138 lb of all-purpose ready-mix (roughly 2.2 cartons of 4.5 gallons) and about 370 ft of paper tape. Lightweight compounds cover more per carton; a level 5 skim coat uses more mud and more labor. Screws are figured at one per sq ft of wall and 1.15 per sq ft of ceiling, at about 300 per pound.

Hanging and finishing are separate production rates, and finishing is where drywall bids go wrong. Price both in the estimate builder, or see how the drywall estimating software packs hang, tape and finish as separate assemblies. Framing and insulation come first — the stud calculator and insulation calculator use the same walls.