How many sheets of drywall do I need?
Total the wall and ceiling area, subtract openings, add 10% waste, then divide by the sheet area. A 4×8 sheet is 32 sq ft, a 4×10 is 40 and a 4×12 is 48.
Quick method: for a room with 8 ft ceilings, multiply the floor area by 3.5 to approximate total drywall area including the ceiling. A 12 × 14 ft room is 168 sq ft of floor, so roughly 588 sq ft of board, which is about 19 sheets of 4×8.
Worked example: a 14 × 12 ft room with 8 ft ceilings has a 52 ft perimeter, so 416 sq ft of wall plus 168 sq ft of ceiling = 584 sq ft. Subtract one door (21) and two windows (30) for 533 sq ft net. Add 10% and divide by 32: 19 sheets.
How the calculation works
Wall area = perimeter × ceiling height. Perimeter = 2 × (length + width). Ceiling area = length × width. Openings are subtracted at 21 sq ft per door and 15 sq ft per window.
Screws are estimated at 36 per sheet — that covers field and perimeter fastening at 16 in on centre. There are roughly 155 of the standard 1¼ in coarse-thread screws per pound.
Joint compound is estimated at one 4.5-gallon bucket per 12 sheets, which covers tape coat plus two finish coats at a level 4 finish. A level 5 skim coat needs roughly 50% more.
Tape is estimated at 24 linear feet per sheet, covering both the long and butt joints plus inside corners.
Typical drywall material cost, mid-2026
| Material | Unit | Typical range |
|---|---|---|
| ½ in regular board | per 4×8 sheet | $12.00 – $18.00 |
| ⅝ in Type X (fire-rated)Required on garage ceilings and shared walls | per 4×8 sheet | $15.00 – $24.00 |
| Moisture-resistant / green board | per 4×8 sheet | $16.00 – $26.00 |
| Cement board (wet areas) | per 3×5 sheet | $12.00 – $22.00 |
| Joint compound | per 4.5 gal bucket | $16.00 – $24.00 |
| Paper joint tape | per 250 ft roll | $3.00 – $6.00 |
| Drywall screws | per 1 lb | $4.00 – $8.00 |
| Hang and finish labour | per sq ft | $1.50 – $3.50 |
What goes wrong on this job
- Hang ceilings first, then walls. The wall sheets push up against the ceiling board and support its edges, which stops the perimeter joints from cracking later.
- Hang board horizontally on walls where you can. It puts the seam at a comfortable 4 ft working height, reduces total joint length by about 25%, and hides the natural bow in studs.
- Use ⅝ in Type X where code requires it — garage ceilings with living space above, and walls between an attached garage and the house. Inspectors check this specifically, and a failure means tearing out finished work.
- Buy longer sheets if you can get them into the room. A 4×12 sheet in a 12 ft room means one continuous wall with zero butt joints, and butt joints are what make amateur drywall look amateur.
- Order 10% waste even on simple rooms. Sheets get damaged in transit, corners break off during handling, and a single bad cut on the last sheet means another trip.
Frequently asked questions
How many drywall sheets for a 12x12 room?
With 8 ft ceilings: 48 ft perimeter × 8 ft = 384 sq ft of wall, plus 144 sq ft of ceiling = 528 sq ft. Less one door and one window, plus 10% waste, that is about 17 sheets of 4×8.
How much joint compound do I need per sheet?
Roughly one 4.5-gallon bucket per 12 sheets for a standard level 4 finish. Budget 50% more if you are skim-coating the whole surface to level 5.
Should drywall be hung horizontally or vertically?
Horizontally for most residential walls — fewer linear feet of joint, seams at a workable height, and it bridges stud irregularities. Vertically for commercial fire-rated assemblies and walls over 9 ft.
How many screws per sheet of drywall?
About 36 for a 4×8 sheet on 16 in centres — roughly every 12 in in the field and every 8 in along the edges. Ceilings need more, closer to 48.