Drywall Calculator
Sheet counts for any room or wall area, plus the screws, joint compound and tape to go with them.
How much drywall do I need?
Work out the wall area from the room perimeter times the ceiling height, subtract doors and windows, add the ceiling if you are boarding it, then divide by the coverage of your sheet size and add waste.
For a 12 by 14 foot room with 8 foot ceilings: the perimeter is 52 feet, times 8 feet is 416 square feet of wall. Subtract 40 square feet for a door and a window and you have 376. Add a 168 square foot ceiling for 544 total. At 10 percent waste that is 598 square feet, which is 19 of the 4 by 8 sheets or 13 of the 4 by 12s.
| Sheet size | Coverage | Sheets for 500 sq ft | Best for |
|---|---|---|---|
| 4 x 8 ft | 32 sq ft | 17 | Tight spaces, stairs, working alone |
| 4 x 9 ft | 36 sq ft | 14 | 9 ft ceilings without a seam |
| 4 x 10 ft | 40 sq ft | 14 | Rooms up to 10 ft, fewer butt joints |
| 4 x 12 ft | 48 sq ft | 11 | Long walls, the fewest seams |
Buy the longest sheet you can handle
The instinct is to buy 4 by 8 sheets because they are easier to carry. On anything but a very small room, that is the wrong call.
Drywall is hung horizontally on walls, and the goal is to minimise butt joints, which are the seams where two sheet ends meet. Butt joints have no tapered edge, so they are much harder to finish flat and they are where you see waves and shadows under a raking light.
On a 12 foot wall, one 12 foot sheet gives you zero butt joints. Using 8 foot sheets gives you a butt joint in the middle of every course. The extra effort of manoeuvring long sheets buys you a noticeably better finish and a lot less sanding.
Screws, mud and tape
Figure about 36 screws per sheet, which covers the field and the perimeter at typical 12 inch spacing. There are roughly 320 screws in a pound of 1.25 inch coarse thread, so a 19 sheet room needs about 684 screws, a bit over 2 pounds. Buy a 5 pound box, you will use them.
For joint compound, a 4.5 gallon bucket of all purpose covers roughly 475 square feet through tape plus three coats. The 544 square foot room above needs two buckets. Buy all purpose unless you have a reason not to. Lightweight compound sands more easily but is weaker for the bedding coat.
Joint tape runs about 370 feet per 1,000 square feet of board. Paper tape is stronger and is what you want for inside corners. Mesh tape is easier for a beginner on flat seams but must be used with setting compound rather than premixed, or the joint will crack.
Which board goes where
- Standard half inch for walls and ceilings in normal rooms.
- Five eighths inch, type X where fire rating is required, usually a garage sharing a wall with living space or a ceiling under living space. Your code will specify it. It is also stiffer and sags less on ceilings with 24 inch framing.
- Moisture resistant for bathrooms and laundry rooms, though not directly behind a shower.
- Cement board behind tile in a shower or tub surround. Drywall of any kind does not belong there.
- Quarter inch flexible for curved walls and arches, usually doubled up.
Waste
Ten percent is right for a normal rectangular room. Push it to 15 percent if you have a lot of windows, angled ceilings, soffits or anything that means cutting around obstacles repeatedly.
One thing worth knowing: do not subtract small openings from your order even though this calculator lets you enter them. A standard door is only about 21 square feet, and you will often board straight over the opening and cut it out afterwards, which is faster and gives cleaner edges. Subtracting openings makes sense for large picture windows and openings over about 25 square feet, but on a typical room leaving them in effectively becomes your waste allowance.
Common questions
How many sheets of drywall do I need for a 12x14 room?
With 8 foot ceilings and one door and window subtracted, about 544 square feet including the ceiling. That is 19 sheets at 4 by 8, or 13 sheets at 4 by 12, with 10 percent waste included.
How many screws per sheet of drywall?
About 36 per 4 by 8 sheet at standard 12 inch spacing, covering both the field and the perimeter. There are roughly 320 screws in a pound of 1.25 inch coarse thread drywall screws.
How much joint compound do I need?
A 4.5 gallon bucket of all purpose compound covers roughly 475 square feet of board through taping plus three coats. A typical bedroom needs two buckets. Buy all purpose for bedding and either all purpose or lightweight for the finish coats.
Should I use 4x8 or 4x12 drywall sheets?
Use the longest sheet you can physically handle. Longer sheets mean fewer butt joints, and butt joints have no tapered edge so they are the hardest seams to finish flat. On a 12 foot wall a single 12 foot sheet eliminates the seam entirely.
Do I subtract doors and windows from drywall calculations?
Only large ones, over about 25 square feet. For standard doors and windows most people board straight over the opening and cut it out after, which is faster and gives cleaner edges. Leaving them in effectively becomes your waste allowance.
These figures are planning estimates. Bulk material weight shifts with moisture and screen size, and suppliers round differently, so confirm the final quantity with your yard before you order.