Drywall Calculator
Estimate a complete drywall job. Work from room dimensions or a total area, subtract doors and windows, pick your sheet size and waste allowance, and get the sheet count plus the joint compound, tape and screws to buy. Turn on the cost estimate for a full material and labor breakdown.
Formula
Worked example
A 14 x 12 ft room with 8 ft ceilings, ceiling included, less 1 door and 2 windows: walls 2 x (14 + 12) x 8 = 416, ceiling 168, minus 21 + 30 openings = 533 sq ft net. At 32 sq ft per 4x8 sheet that is 16.7 sheets, plus 10% waste rounds up to 19 sheets.
How the drywall estimate works
Drywall is sold as flat rectangular sheets, so the estimate divides the surface area you want to cover by the area of one sheet. In room mode the calculator finds the wall area as the room perimeter, which is two times length plus width, multiplied by the ceiling height, then adds the ceiling if you are boarding it. It subtracts a standard allowance for each door (about 21 square feet) and window (about 15 square feet). In area mode you simply enter a total you have already measured. Either way the net area is divided by the sheet coverage, multiplied by a waste factor, and rounded up, because you cannot buy a fraction of a sheet.
Sheet sizes and measuring correctly
Standard panels are 4 feet wide and come in 8, 9, 10 and 12 foot lengths, covering 32, 36, 40 and 48 square feet. Longer sheets leave fewer seams to tape and finish for a smoother wall, but they are heavy and awkward in tight or upstairs rooms, so 4 by 8 is the usual DIY choice. Measure each wall as width times height and a ceiling as length times width. Many estimators leave small openings in the area because the off-cuts around them are rarely reusable, which builds a natural buffer; this calculator subtracts only full-size doors and windows, so lean toward a higher waste percentage if your room has many openings.
Joint compound, tape and screws
Boards alone do not finish a wall. As a rule of thumb a job uses roughly 72 pounds of all-purpose joint compound and about 400 feet of paper or mesh tape per 1000 square feet of board, which works out to a 4.5 gallon bucket of premixed mud for every 250 to 300 square feet. Screws land at roughly one per square foot, about 32 per 4 by 8 sheet when you fasten the field and edges to code. The calculator reports all three so you can add them to your buy list, and you should round up to whole buckets, rolls and boxes at the store.
Costing the job
Turn on the cost estimate to price the work. Standard half inch board runs about 10 to 14 dollars per 4 by 8 sheet, and joint compound, tape, corner bead and fasteners together add roughly 0.15 to 0.30 dollars per square foot. Add installation labor to include hanging and a Level 4 finish, which averages 1.50 to 2.50 dollars per square foot nationally and more in coastal metros. The total is a planning figure; local prices, finish level and delivery all vary, so confirm against quotes before you commit. The cost split donut shows how much of the total is materials versus labor.
Coverage and materials by sheet size
| Sheet size | Coverage per sheet | Sheets per 1000 sq ft | Mud per 1000 sq ft | Tape per 1000 sq ft |
|---|---|---|---|---|
| 4 ft x 8 ft | 32 sq ft | 32 | ~72 lb | ~400 ft |
| 4 ft x 9 ft | 36 sq ft | 28 | ~72 lb | ~400 ft |
| 4 ft x 10 ft | 40 sq ft | 25 | ~72 lb | ~400 ft |
| 4 ft x 12 ft | 48 sq ft | 21 | ~72 lb | ~400 ft |
Square feet covered per sheet and the companion materials per 1000 sq ft of board.
Frequently asked questions
Should I subtract doors and windows from the area?
In room mode this calculator subtracts a standard allowance of about 21 square feet per door and 15 square feet per window. Many pros leave small openings in, because the off-cuts around them are rarely reusable and counting the full wall builds a buffer. If you subtract openings, use a slightly higher waste percentage to stay safe.
How much joint compound and tape do I need?
A common rule of thumb is about 72 pounds of all-purpose compound and 400 feet of tape per 1000 square feet of board, or roughly one 4.5 gallon bucket of premixed mud per 250 to 300 square feet. The calculator estimates both from your board area, and you should round up to whole buckets and rolls.
How much waste should I add?
Ten percent is the common default for a simple, boxy room. Use about 15 percent for spaces with many corners and openings, and up to 20 percent for soffits, arches or angled ceilings, since those produce more unusable off-cuts. Rounding up to whole sheets already adds a small cushion.
How much does it cost to drywall a room?
Materials run roughly the sheet price plus 0.15 to 0.30 dollars per square foot for compound, tape and fasteners. Adding professional hang and a Level 4 finish typically pushes the all in figure to about 1.50 to 3.00 dollars per square foot. Turn on the cost estimate to price your specific room with your own rates.
Are larger 4 by 12 sheets better than 4 by 8?
Larger 4 by 12 sheets cover more area with fewer seams to tape and finish, which gives a smoother wall and less labor. They are heavy and awkward in tight or upstairs rooms though, so 4 by 8 sheets are easier to carry and cut for a DIY project.