How to use the drywall calculator
- Enter the room length, width and wall height in feet.
- Leave the ceiling checked if you are hanging it too. The calculator counts ceiling sheets and screws separately because ceilings use closer screw spacing.
- Count the doors and windows with their sizes, or enter the total opening area. Enter 0 to skip the deduction.
- Pick the sheet size, the waste allowance and the framing spacing.
Drywall formulas
Wall area = 2 × (length + width) × height Ceiling area = length × width Openings = Σ (width × height) ÷ 144 (sizes in inches) Net area = wall area − openings + ceiling area Sheets = area × (1 + waste %) ÷ sheet area, rounded up Screws = sheets × screws per sheet Compound (gal) = net area ÷ 1,000 × 10 Tape (ft) = net area ÷ 1,000 × 370
Walls and ceiling are rounded up separately, since you hang them as separate runs. Compound and tape are based on the net board area, without the waste allowance.
Worked example
A 12 x 12 ft bedroom with 8 ft walls, the ceiling, one 36 x 80 in door and one 36 x 48 in window, 4x8 sheets, 10% waste and framing at 16 in on center.
- Wall area: 2 × (12 + 12) × 8 = 384 sq ft.
- Ceiling area: 12 × 12 = 144 sq ft.
- Openings: (36 × 80 + 36 × 48) ÷ 144 = 32 sq ft.
- Net wall area: 384 − 32 = 352 sq ft. Net board area: 496 sq ft (46.08 m²).
- Wall sheets: 352 × 1.10 ÷ 32 = 12.1, so 13 sheets.
- Ceiling sheets: 144 × 1.10 ÷ 32 = 4.95, so 5 sheets. Total: 18 sheets.
- Screws: 13 × 28 + 5 × 35 = 539 screws, about 3 lb at 250 per pound.
- Joint compound: 496 ÷ 1,000 × 10 = 4.96 gal, so two 4.5 gal pails.
- Tape: 496 ÷ 1,000 × 370 = 184 ft, so one 250 ft roll.
Where the material rates come from
- Joint compound: about 10 gal per 1,000 sq ft of board, from the USG Sheetrock All Purpose Joint Compound submittal sheet (ready-mixed, sold in 4.5 gal pails). USG lists lightweight compounds at about two 4.5 gal pails per 1,000 sq ft. Setting-type powders and other brands differ, so check the bag or pail.
- Tape: about 370 ft per 1,000 sq ft, from the USG Sheetrock Paper Joint Tape submittal sheet. Rolls come in 75, 250 and 500 ft.
- Screws: spacing from IRC Table R702.3.5 for 1/2 and 5/8 in board without adhesive: 12 in on ceilings, 16 in on walls framed at 16 in, 12 in on walls framed at 24 in. Screws per sheet assume the sheet runs across the framing, with a screw at each edge of every framing member it crosses. A 4x8 on wall studs at 16 in takes 7 × 4 = 28 screws, and on ceiling joists 7 × 5 = 35.
- Waste: 10% for rooms with long, simple walls and 15% for rooms with many corners, openings, soffits or angled ceilings. These are common rules of thumb, not a published standard.
Tips
- Hang the ceiling first, then the walls, so the wall sheets hold up the ceiling edges.
- Longer sheets mean fewer joints to tape. A 12 ft wall takes one 4x12 per row instead of a 4x8 plus a cut piece.
- For a ceiling that gets a water-based texture on framing at 24 in, the IRC calls for 5/8 in board or 1/2 in sag-resistant ceiling board.
- A garage ceiling under a living space needs 5/8 in Type X board with fasteners at 6 in, which takes more screws than this calculator assumes.