Drywall Calculator
Sheets, screws, tape and mud are one purchase, not four. Enter the room and get the whole load — including the 10% you will lose to outlet cutouts and odd corners.
Reviewed · Method: measured area + industry waste allowance, rounded up to real package sizes · How the numbers are calculated
Enter your dimensions and hit Calculate my drywall order. You will get the quantity, the buyable quantity, a shopping list, and a budget range.
Figure. Wall and ceiling area, a cutting allowance, then division by the sheet size you actually plan to buy.
Figure. Use the room perimeter for walls and the floor rectangle for the ceiling. Add 10% for cuts around openings.
Sheets, then everything the sheet needs
Wall area is the perimeter times height; ceiling area is length times width. The total is divided by the sheet size and rounded up with a 10% cutting allowance. Then the accessories are derived from the sheet count: about 32 screws per 4x8 sheet at 12-inch spacing on studs, one pound of joint compound per 10 sq ft of board over three coats, and roughly 1.2 linear feet of tape per square foot of board.
Longer sheets mean less work
A 4x12 sheet covers 50% more area than a 4x8 and removes several butt joints. Butt joints are the hardest seams to hide because there is no tapered edge to bury the tape in. If your stairwell and doorways allow a 12 ft sheet through, the extra material cost is usually repaid by a faster finish. This tool switches sheet size without changing anything else, so you can compare.
Ceilings want 5/8 inch
Half-inch board sags between joists on 24-inch centers over time, especially under attic insulation. Five-eighth inch is the standard for ceilings and any wall that needs a fire rating, like a garage separation. It weighs about 25% more per sheet, so plan two people for anything overhead.
What the estimate excludes
Corner bead, studs, insulation, and any framing repair. Add one 8 ft vinyl corner bead per outside corner, and count studs separately at 16-inch centers. If you are removing old drywall, disposal is a real cost — a 12x16 room typically produces about 500 lb of debris.
How sheet size changes the total
Board area is fixed, but sheet size decides how much of it you throw away. A 4x8 sheet is 32 sq ft; a 4x12 is 48 sq ft. On a 16 ft wall, two 4x8 sheets leave a 8 ft seam in the middle. One 4x12 plus one 4x8 covers more with fewer butt joints, at a higher price per sheet.
The rule that matters: joints cost labour, not material. Fewer butt joints means less taping, less mud, and a flatter wall. Price the 4x12 before you commit to the cheaper 4x8, especially on ceilings where joints are hardest to finish.
Hanging order and the one-third rule
Hang ceilings first, then walls, so the wall board supports the ceiling edges. Stagger vertical joints between rows by at least one stud bay; four corners meeting at one point is the single hardest detail to finish and the first place a crack appears.
Fasteners go every 12 in on ceilings and every 16 in on walls, with a screw 3/8 in from each edge. Add a screw wherever two sheets meet, because that is where the board wants to move.
Worked example: 16 x 12 ft room, 8 ft ceiling, 4x8 sheets
| Wall area | 2 x (16 + 12) x 8 = 448 sq ft |
| Ceiling | 16 x 12 = 192 sq ft |
| Total board | 640 sq ft including the cut allowance |
| Sheets at 32 sq ft | 640 / 32 = 20, plus 2 for cuts |
| Screws | 704 pieces |
| Joint compound | 2 buckets of 4.5 gal |
| Tape | 768 linear ft |
| Budget band | $366 low, $480 mid, $645 high |
Mistakes that cost real money
Forgetting the ceiling
A 16 x 12 ft room adds 192 sq ft of board for the ceiling, which is six sheets. Rooms are commonly estimated on walls alone, and the shortfall only becomes obvious after the walls are hung and the ceiling is still open.
Buying 8 ft sheets for an 8 ft wall
Walls are rarely exactly 8 ft after framing and flooring. A 4x8 sheet stood vertically leaves a strip at the top or bottom that is slow to finish and weak. Measure the actual height first, and price 4x12 sheets if the ceiling allows it.
Under-buying joint compound
Three coats over new board uses far more mud than people expect: roughly one gallon per 100 sq ft of board. Buying a bucket at a time means a second trip, and a different batch of mud can sand differently on the final pass.
Screwing too close to the edges
Screws need to sit about 3/8 in from the board edge and be driven just below the surface without breaking the paper. Over-driven screws pop through and every one of them becomes a call-back after the paint goes on.
Ignoring what is behind the wall
The calculator cannot see stud spacing, insulation, or old plaster that has to come down. A room with 24 in stud spacing needs thicker board or a re-frame, and that changes both the sheet count and the budget by more than the board itself.
Frequently asked questions
How many sheets of drywall for a 12x12 room?
About 13 sheets of 4x8 for walls and ceiling with 10% waste, assuming 8 ft ceilings. That is 416 sq ft of wall plus 144 sq ft of ceiling, or 560 sq ft total.
How many screws per sheet of drywall?
Roughly 32 screws per 4x8 sheet with fasteners every 12 inches on studs and edges. Ceilings use more, typically 40 to 48 per sheet.
How much joint compound do I need?
About one pound per 10 sq ft of drywall for a three-coat finish. A 12x12 room with ceiling needs roughly two 4.5 gallon buckets.
Do I need special drywall in a bathroom?
Yes. Use moisture-resistant board in the bathroom and cement board in any wet area behind tile. Standard board will grow mold in a humid bathroom within a couple of years.
Should I add 10% waste to drywall?
Yes. Outlet boxes, window returns and corner cuts consume material that cannot be reused. Ten percent is the standard allowance; complex rooms with many openings can need 15%.