Drywall Calculator
Count the drywall sheets, pails of joint compound, rolls of tape and screws a room needs from its size, doors and windows, with the ceiling as an option.
Drywall is four things to buy, and the store sells them in four different units: sheets, pails of joint compound, rolls of tape and boxes of screws. This turns the room into a shopping list from the makers' own coverage figures, with the cuts and breakage already counted.
The room
Measure wall to wall. A bedroom is about 12 × 12; a basement family room might be 24 × 16. For an L-shaped room, run each rectangle separately and add.
Room length
Room width
Ceiling height
Drywalling the ceiling too?
Doors and windows
Openings come off the wall area. Count every doorway, closets included, and every window.
Doors
Windows
Sheet size
Both are half-inch board. Longer sheets mean fewer seams to tape, but a 4 × 12 weighs about 80 pounds and won't fit in most cars.
4 × 8 sheets to buy
12 sheets
349 sq ft of wall after 2 openings, plus 10 percent for cuts
What the 10 percent covers, and what it doesn't
Ten percent extra is the cuts around the door and window, the piece that breaks going through the doorway, and the strip you measure wrong. It's enough for a plain rectangular room. A closet, a knee wall, an angled ceiling or a room full of windows wastes 15 to 20 percent, so add a sheet or two there. Buy the compound in a pail rather than a box if you'll be finishing over more than a weekend; the pail reseals. And hang sheets horizontally, tapered edges together, so the seams are at a height you can finish without a ladder.
Wall area is the perimeter times the height, less 20 sq ft a door and 15 a window, plus the ceiling if included; sheets are that area plus 10 percent, divided by 32 for a 4 × 8 or 48 for a 4 × 12. Compound is the maker's 10 gallons per 1,000 sq ft, tape 370 feet per 1,000, screws one per square foot on walls and 1.1 on ceilings from the standard spacing. 2026 figures.
💡About this calculator▼
Drywalling a room means buying four things sold in four different units: sheets by the piece, joint compound by the pail, tape by the roll, screws by the box. The sheets are the easy part; it's the mud and the tape people run out of on a Sunday afternoon, because the coverage figures are printed per thousand square feet on the side of a pail.
This makes the list. Enter the room's length, width and ceiling height, count the doors and windows, say whether the ceiling is being done too, and pick a sheet size. You get the sheets with cuts and breakage already counted, the compound in pails, the tape in rolls and the screws, all from the makers' own coverage figures.
The ceiling changes more than the count. It adds about a third to a bedroom's material, takes a denser screw pattern, and is the hardest lift in the job, which is why the calculator handles it separately and the box below tells you to hang it first.
Start with the wall area. The perimeter of the room times the ceiling height, less about 20 square feet for each door and 15 for each window. A 12 by 12 room with 8-foot ceilings is 384 square feet of wall; one door and one window take it to 349.
Add the ceiling if you're doing it. Length times width, 144 square feet for that room.
Turn area into sheets. Add 10 percent for cuts and breakage, then divide by the sheet: 32 square feet for a 4 × 8, 48 for a 4 × 12, rounded up. The 12 by 12 room needs 12 sheets of 4 × 8 for the walls, 17 with the ceiling.
Add the finishing materials from the makers' figures. All-purpose joint compound covers about 10 gallons per 1,000 square feet of board for taping and three coats, and comes in 4.5-gallon pails. Paper tape covers about 370 feet per 1,000 square feet, in 500-foot rolls. Screws follow the standard spacing, one every 16 inches on wall studs and every 12 on ceiling joists, which works out to about one screw per square foot of wall and 1.1 per square foot of ceiling.
Worked example. The 12 by 12 room, 8-foot walls, one door, one window, walls only: 349 square feet; × 1.1 ÷ 32 = 12 sheets; 3.5 gallons of compound, one pail; 129 feet of tape, one roll; about 350 screws. With the ceiling: 493 square feet, 17 sheets, two pails, one roll, about 510 screws.
📐How it's calculated▼
Wall area = 2 × (length + width) × height − 20 × doors − 15 × windows. Ceiling area = length × width if included.
Sheets = (wall + ceiling) × 1.10 ÷ 32 for a 4 × 8, ÷ 48 for a 4 × 12, rounded up.
Compound = area × 10 gallons ÷ 1,000, in 4.5-gallon pails, rounded up. Tape = area × 370 feet ÷ 1,000, in 500-foot rolls, rounded up.
Screws = wall area × 1.0 + ceiling area × 1.1, rounded to ten.
Default (12 × 12 × 8, 1 door, 1 window, 4 × 8, walls only): 384 − 35 = 349 sq ft → 12 sheets, 3.5 gal (1 pail), 129 ft (1 roll), 350 screws.
With the ceiling: 493 sq ft → 17 sheets, 4.9 gal (2 pails), 182 ft (1 roll), 510 screws.
Basement family room 24 × 16 × 8, 2 doors, 2 windows, ceiling: 954 sq ft → 33 sheets of 4 × 8 or 22 of 4 × 12, 3 pails, 1 roll, about 990 screws.
📎Sources:USG — Sheetrock Brand All Purpose Joint Compound submittal sheet (coverage ~10 gal per 1,000 sq ft, pail sizes),USG — Sheetrock Brand Paper Joint Tape submittal sheet (coverage ~370 ft per 1,000 sq ft, 500-ft rolls),Gypsum Association — GA-216 Application and Finishing of Gypsum Panel Products (screw spacing for walls and ceilings)
🔍Finding your inputs▼
Room length, width and ceiling height: Wall to wall and floor to ceiling, in feet. Most rooms are 8 feet high, which is why a sheet is 8 feet long. For an L-shaped room, run each rectangle and add the results.
Drywalling the ceiling too: Yes for new construction or a gutted room; no if the ceiling is staying. The ceiling adds its area, uses the denser screw spacing, and gets hung first.
Doors and windows: Count every doorway, closets included, and every window; each door takes about 20 square feet off the wall area and each window about 15. Count a big picture window or a patio door as two.
Sheet size: A 4 × 8 sheet is about 50 pounds, fits in a car with the seats down and one person can hang it on a wall. A 4 × 12 is about 80 pounds and needs two people and a delivery, but on long walls it cuts the seams you have to tape by a third. Both are half-inch board.
⚠️Special situations▼
How many sheets of drywall do I need for a 12 × 12 room?
Twelve 4 × 8 sheets for the walls with one door and one window, or 14 if you don't subtract the openings, which is the figure most people quote. Add the ceiling and it's 17. In 4 × 12 sheets it's 8 for the walls and 12 with the ceiling. The difference between 12 and 14 is what a door and a window take out, and the 10 percent cut allowance is already in both numbers.
The manufacturer's calculator gave me more sheets than this.
The makers' tools don't subtract doors and windows; that's their built-in waste allowance. This calculator subtracts the openings and adds 10 percent instead, which lands within a sheet of theirs on a normal room and closer to what actually goes on the wall. If your room is a closet, has a knee wall or an angled ceiling, or has windows on every wall, use the higher number, because cutting around all of that wastes 15 to 20 percent.
How much mud do I really need? The pail says 1,000 square feet.
About 10 gallons of all-purpose compound per 1,000 square feet of board, for taping and three finish coats, which is the maker's own figure. A 4.5-gallon pail covers about 450 square feet, so a 12 × 12 room's walls take most of one pail and the walls plus ceiling take most of two. If you're skim-coating the whole surface for a smooth finish, plan on about double, and buy the first coat as setting-type compound in a bag if you want to finish in a day.
Do I need 5/8-inch drywall?
Usually only on a ceiling with joists 24 inches apart, where half-inch board sags, and on a garage wall shared with the house, where code wants the fire rating. Everywhere else half-inch is standard, and the counts here don't change with thickness; only the weight does, from about 50 to about 70 pounds a 4 × 8. Screws for 5/8 board should be 1⅝ inch instead of 1¼.
❓Common questions▼
How do I calculate how much drywall I need?
Measure the room's perimeter and multiply by the ceiling height for the wall area, subtract about 20 square feet per door and 15 per window, add the ceiling area if you're doing it, add 10 percent for cuts, and divide by 32 for 4 × 8 sheets or 48 for 4 × 12. A 12 × 12 room with 8-foot ceilings, a door and a window is 349 square feet of wall and 12 sheets; with the ceiling, 493 square feet and 17 sheets.
How much joint compound do I need per sheet of drywall?
About a third of a gallon per 4 × 8 sheet for taping and three coats, from the maker's coverage of roughly 10 gallons per 1,000 square feet of board. A 4.5-gallon pail finishes about 14 sheets, which is a 12 × 12 room's walls with a little left over. Skim coating or a level-5 finish roughly doubles it.
How many drywall screws per sheet?
About 28 to 32 for a 4 × 8 sheet on a wall and about 35 on a ceiling, from the standard spacing of one screw every 16 inches on wall studs and every 12 on ceiling joists, on framing 16 inches apart. That's about one screw per square foot of wall and 1.1 per square foot of ceiling, so a 12 × 12 room's walls take about 350 and the ceiling adds about 160. A 1-pound box of 1¼-inch coarse-thread screws holds roughly 300.
Should I buy 4 × 8 or 4 × 12 sheets?
4 × 8 if you're carrying them yourself: about 50 pounds, fits a car with the seats down, one person can hang it on a wall. 4 × 12 if a long wall is involved and you have help: about 80 pounds and 12 feet, but a 12-foot wall gets one seam instead of two, and every seam is a joint to tape, mud three times and sand. Hang either one horizontally, so the tapered long edges meet at waist height.
How much tape do I need for drywall?
About 370 feet per 1,000 square feet of board, the maker's figure, so a 12 × 12 room's walls take about 130 feet and the walls plus ceiling about 180. One 500-foot roll of paper tape does nearly any single room, and a big basement with the ceiling needs two. Paper tape is the standard; mesh tape is for setting-type compound and repairs.
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