How the calculator works
It adds the area of every wall (length × height) and ceiling (length × width), subtracts doors and windows, and divides by the area of one sheet. Drywall panels are 4 feet wide, so a 4×8 sheet covers 32 sq ft, a 4×10 covers 40 and a 4×12 covers 48. It then adds your waste allowance and rounds up: sheets = round up(net area ÷ sheet area × (1 + waste %)).
As a cross-check it also counts sheets the way you would hang them, row by row, assuming no offcut gets reused. That full-sheet layout count is an upper bound. If it is much higher than the area estimate, your walls are short or chopped up and you should buy closer to it.
Finishing supplies
Screws, tape, joint compound and primer come from the estimating table in USG's Sheetrock installation and finishing guide, scaled to your area. USG notes that compound coverage can vary widely with the condition of the surface, the tools and the method.
| Item | Amount | Assumption |
|---|---|---|
| Type W drywall screws | 2.7 lb | Spaced 12 in on ceilings, 16 in on walls |
| Joint tape | 370 ft | USG Sheetrock paper joint tape |
| All-purpose joint compound | 10.0 gal | Ready-mix; covers flat joints, inside and outside corners |
| Lightweight all-purpose compound | 9.0 gal | Alternative to the line above |
| Drywall primer | 2.5 gal | Assumes 400 sq ft per gallon |
Worked example: a 14 × 12 ft bedroom
- Walls: two at 14 × 8 ft (224 sq ft) and two at 12 × 8 ft (192 sq ft). Ceiling: 14 × 12 ft (168 sq ft). Total 584 sq ft.
- Subtract one door (21 sq ft) and one window (15 sq ft): 548 sq ft to cover.
- 4×8 sheets: 548 ÷ 32 = 17.1 sheets. Add 10% waste: 18.8, rounded up to 19 sheets.
- Supplies at 0.548 × the USG rates: 1.5 lb of screws, 203 ft of tape, 5.5 gallons of all-purpose compound (two 4.5-gallon pails) and 1.4 gallons of primer.
- At the example prices ($16 a sheet, $22 a pail, $6 a tape roll, $9 per lb of screws): about $372 in materials.
Hanging full sheets with no offcut reuse would take 22: 16 for the walls (each 8 ft high wall needs two horizontal rows, and a 14 or 12 ft wall needs two 8 ft sheets per row) plus 6 for the ceiling (three rows of two). Switch to 4×12 sheets and the area estimate drops to 13 sheets with fewer end joints to tape.
Choosing a sheet size and direction
USG's guide says horizontal application with 12 ft panels is ideal for walls because it minimizes the length of joints, and it recommends the longest panels available with end joints offset between rows. Longer sheets are heavier and harder to get up stairs and around corners, which matters in walk-ups and small elevators. The UltraLight panel submittal lists 4 ft and 54 in widths and lengths from 8 to 16 ft, so ask your supplier what they stock.
What to do next
Check whether your project needs a permit in Do you need a DOB permit? and read renovating a co-op or condo if you live in one. Once the walls are up, use the paint calculator (new drywall needs primer), and size the room with the square footage calculator.