Drywall Calculator
Enter a room's dimensions to find out how many sheets of drywall you need, in 4x8 or 4x12 foot panels, plus joint compound, tape, and screws. Doors and windows are subtracted automatically. Results update as you type. Need paint or flooring instead? Try the paint calculator or the flooring calculator.
- Net drywall area
- 0 ft²
- With waste factor
- 0 ft²
- Joint compound needed
- 0 gal
- Tape needed
- 0 ft
How to measure a room for drywall
Measure the length of each wall at floor level with a tape measure, and add them together to get the room's perimeter; for a simple rectangle that is twice the length plus twice the width. Measure the wall height from floor to ceiling, then multiply the perimeter by the height to get the gross wall area, which is the starting figure this calculator works from before subtracting anything.
Doors and windows do not get drywalled, so their area comes back out. This calculator uses the same door (20 square feet) and window (15 square feet) deductions as this site's paint calculator, for consistency; adjust the counts if your room has more or fewer than one of each, or measure and subtract unusually large openings by hand.
Pick whether you are drywalling the ceiling in the same pass. If so, check "include ceiling" to add the room's floor-equivalent area (length times width) to the wall total. If the ceiling is being hung on a separate schedule, leave it unchecked and run the ceiling as its own calculation.
Standard drywall sheets come in 4x8 (32 square feet) and 4x12 (48 square feet) sizes; this calculator shows sheet counts for both so you can compare. Larger 4x12 sheets mean fewer seams to tape and finish but are heavier to maneuver alone, especially overhead on a ceiling.
Always add a waste factor on top of the raw area. 10 percent is a reasonable default for a straightforward rectangular room; rooms with lots of corners, high ceilings that need extra cuts, or a less experienced crew often use 15 percent or more. This calculator rounds the sheet count, joint compound, and tape up to the next whole sheet, gallon, or roll, since none of those are sold in exact fractions.
Worked example
A room measures 12 ft by 12 ft with 8 ft walls, 1 door, 1 window, no ceiling included, and 10% waste.
Perimeter = 2 × (12 + 12) = 48 ft.
Gross wall area = 48 × 8 = 384 sq ft.
Doors and windows to subtract = (1 × 20) + (1 × 15) = 35 sq ft.
Net drywall area = 384 − 35 = 349 sq ft.
With 10% waste: 349 × 1.10 = 383.9 sq ft total to order.
Sheets needed (4x8, 32 sq ft each) = 383.9 ÷ 32 = 11.997 exact, rounded up to 12 sheets.
Sheets needed (4x12, 48 sq ft each) = 383.9 ÷ 48 = 7.998 exact, rounded up to 8 sheets.
Joint compound (USG All Purpose, 1.0 gal per 100 sq ft) = 383.9 ÷ 100 × 1.0 = 3.839 gal exact, rounded up to 4 gallons.
Tape (USG Paper Joint Tape, 37 ft per 100 sq ft) = 383.9 ÷ 100 × 37 = 142.04 ft exact, rounded up to 143 ft, or 1 roll of 250 ft tape.
Screws (trade estimate, 32/sheet for 4x8 or 48/sheet for 4x12) = 12 × 32 = 384 screws, or equivalently 8 × 48 = 384 screws for the 4x12 option.
Frequently asked questions
How many sheets of drywall do I need for a 12x12 room?
A 12 by 12 foot room with 8 foot walls, one door, and one window needs 349 square feet of drywall before waste. With a 10 percent waste factor that is 383.9 square feet, which needs 12 sheets of standard 4x8 (32 square foot) panels, or 8 sheets of 4x12 (48 square foot) panels, each rounded up since you cannot buy a partial sheet. See the worked example above for the full arithmetic.
Should I use 4x8 or 4x12 drywall sheets?
4x12 sheets cover more area per sheet (48 square feet versus 32), which means fewer seams to tape and finish on a long wall, but they are heavier and harder for one person to maneuver and lift into place, especially on ceilings. 4x8 sheets are easier to handle alone and fit through standard doorways without cutting. This calculator shows both options so you can compare sheet count directly.
How much should I subtract for doors and windows when calculating drywall?
This calculator subtracts a standard door (20 square feet) and window (15 square feet) area for every door and window you enter, the same convention used by this site's paint calculator. Adjust the counts for your actual room, and treat unusually large openings, such as sliding doors or picture windows, as a reason to measure and subtract the exact opening size by hand instead.
How much joint compound do I need per sheet of drywall?
USG's published Sheetrock Brand Installation and Finishing Guide lists approximately 1.0 gallon of All Purpose Joint Compound per 100 square feet of panel for a typical room, covering the flat joints, inside corners, and outside corners with metal corner bead. For a single 4x8 sheet (32 square feet) that works out to about 0.32 gallons; this calculator totals the figure across your whole room and rounds up to a whole gallon.
How many screws per sheet of drywall do I need?
A widely used trade estimate is about 32 screws for a 4x8 sheet on walls framed 16 inches on center, consistent with the Gypsum Association's GA-216 fastener spacing standard (screws every 8 inches along panel edges, every 12 inches in the field). This is an estimate, not an exact manufacturer count, since actual totals range from about 28 to 44 screws per sheet depending on whether the sheet is hung horizontally or vertically and whether it is on a wall or ceiling.
Do I include the ceiling when calculating drywall for a room?
Only if you are drywalling the ceiling in the same pass as the walls. Check "include ceiling" above to add the room's floor-equivalent area (length times width) to the wall total. If the ceiling is being done separately, such as on a different schedule or by a different crew, leave it unchecked and run the calculator again with just the ceiling's own length and width.