Drywall Calculator: How Many Sheets of Drywall Do I Need?

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Whether you use our drywall calculator or a pencil, divide the area you are covering by the area of one sheet, then add about 10 percent for cuts. A 4 x 8 sheet covers 32 sq ft and a 4 x 12 sheet covers 48 sq ft. For example, a 12 x 10 ft room with 8 ft walls, one door, and one window needs 11 sheets of 4 x 8 drywall for the walls, or 16 sheets if you also do the ceiling.

Enter your room below. The calculator subtracts doors and windows, adds the ceiling if you check the box, and rounds up to whole sheets.

How many drywall sheets do you need?

Enter the room size. We subtract doors and windows and add extra for cuts.

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Common sheet sizes are 4 by 8 ft (32 sq ft) and 4 by 12 ft (48 sq ft). We add 10 percent for cuts.

How to measure a room for drywall

  1. Measure the room length and width. Measure along the floor between the framing (or the old wall surface) in both directions. Round up to the next half foot.
  2. Measure the wall height. Go from the subfloor to the underside of the ceiling framing. An 8 ft wall takes exactly two 4 ft sheets hung horizontally; a 9 ft wall needs a filler strip or a wider panel.
  3. Count the doors and windows. The calculator removes 20 sq ft per door and 15 sq ft per window. A wide opening like a double door or a slider is closer to two doors.
  4. Pick a sheet length. The calculator assumes 4 ft wide sheets and lets you choose the length. Try the length that matches your longest wall; fewer end joints means less taping.
  5. Decide on the ceiling. Check "Include the ceiling" to add length x width. If the ceiling needs a different thickness than the walls, run it as a separate estimate so you buy the right board.

The formula (with a worked example)

  • Wall area = 2 x (length + width) x height, minus 20 sq ft per door and 15 sq ft per window
  • Surface = wall area, plus length x width if the ceiling is included
  • Area to buy = surface x 1.10 (10 percent for cuts)
  • Sheets = area to buy / (4 x sheet length), rounded up

Here are the calculator's default values worked by hand: a 12 x 10 ft room, 8 ft walls, 1 door, 1 window, 4 x 8 sheets, ceiling not included.

  1. Perimeter: 2 x (12 + 10) = 44 ft
  2. Gross wall area: 44 x 8 = 352 sq ft
  3. Openings: 20 + 15 = 35 sq ft
  4. Surface: 352 - 35 = 317 sq ft
  5. With 10 percent for cuts: 317 x 1.10 = 348.7, shown as 349 sq ft
  6. Sheets: 348.7 / 32 = 10.9, rounded up to 11

The calculator shows "You need 11 sheets of 4 × 8 ft drywall." with a surface of 317 sq ft and 349 sq ft including the extra. Check the ceiling box and the surface becomes 437 sq ft, or 481 sq ft with extra, which is 16 sheets of 4 x 8. Switch the sheet length to 12 and the same room needs 8 sheets for the walls alone.

Drywall sheets on the walls, and the sheet mathTwo walls of a 12 by 10 foot room with 8 foot walls, covered with 4 by 8 foot drywall sheets (32 sq ft each). The 12 ft wall takes 3 sheets; the 10 ft wall takes 2 and a half, leaving a 2 ft offcut. The window (15 sq ft) and door (20 sq ft) are subtracted: 352 minus 35 is 317 sq ft, plus 10 percent for cuts is 349 sq ft, divided by 32 is 10.9, so buy 11 sheets.WALL AREA TO SHEETSoffcut−15sq ft−20sq ft1 sheet4 × 8 ft32 sq ft½12 ft10 ft8 ft317 sq ft352 wall − 35 openings× 1.1349 sq ft+10% for cuts÷ 3211 sheets10.9, rounded up
Each 4 x 8 ft sheet covers 32 sq ft, so 317 sq ft of wall plus 10% for cuts (349 sq ft) needs 11 sheets.

Drywall sheets by room size

This chart uses the calculator's formula with 8 ft walls, one door, one window, and 10 percent extra.

Room sizeWall surfaceWalls: 4 x 8Walls: 4 x 12Walls + ceiling: 4 x 8Walls + ceiling: 4 x 12
10 x 10 ft285 sq ft107149
12 x 10 ft317 sq ft1181611
12 x 12 ft349 sq ft1281712
14 x 12 ft381 sq ft1491913
16 x 14 ft445 sq ft16112316
20 x 15 ft525 sq ft19132919

Drywall sheet sizes and what they cover

Standard drywall is 4 ft wide. USG lists its lightweight half-inch panels in 48 in and 54 in widths and lengths from 8 to 16 ft, at a nominal 1.25 lb per sq ft.

Sheet sizeCoverageApprox. weight (1/2 in lightweight)Good for
4 x 8 ft32 sq ftAbout 40 lbSmall rooms, closets, working alone
4 x 10 ft40 sq ftAbout 50 lbWalls around 10 ft long
4 x 12 ft48 sq ftAbout 60 lbLonger walls and ceilings with fewer seams
4 x 16 ft64 sq ftAbout 80 lbLong runs where access allows
54 in x 12 ft54 sq ftAbout 68 lbTwo rows cover a 9 ft wall

Weights are calculated from USG's nominal 1.25 lb per sq ft for its UltraLight panels. Other panels, especially thicker 5/8 in boards, can weigh more, so check the label before you plan how to get them into the house.

Thickness: what the code says

The International Residential Code (IRC) sets minimum drywall thickness by location and framing spacing in Table R702.3.5. A summary of the rows for applications without adhesive:

ThicknessLocationMaximum framing spacing
3/8 inCeiling16 in on center, perpendicular to framing only
3/8 inWall16 in on center, either direction
1/2 inCeiling16 in on center either direction; 24 in on center perpendicular only
1/2 inWall24 in on center, either direction
5/8 inCeiling16 in on center either direction; 24 in on center perpendicular only
5/8 inWall24 in on center, either direction

A footnote to that table matters for ceilings: if a ceiling will get a water-based texture, the minimum goes up to 1/2 in on 16 in framing and to 5/8 in on 24 in framing. Manufacturers also make sag-resistant half-inch ceiling panels; USG states its UltraLight panels can take water-based texture on ceilings framed up to 24 in on center. Local codes can differ, so confirm with your building department, especially for garages, fire-rated walls, and wet areas.

Finishing materials: mud, tape, and screws

Once you know the square footage, the finishing supplies follow from it. Use the surface number from the calculator, not the number with extra.

  • Joint compound: USG estimates about 10 gallons of its all-purpose ready-mixed compound per 1,000 sq ft of board. Lowe's estimator lands close, at about 9 gallons per 1,000 sq ft.
  • Paper tape: about 370 ft per 1,000 sq ft, according to USG. Rolls come in 75, 250, and 500 ft lengths.
  • Screws: Lowe's estimator lists about 1,250 screws per 1,000 sq ft. IRC Table R702.3.5 sets maximum screw spacing at 12 in on ceilings and 16 in on walls framed 16 in on center.

For the default 317 sq ft room, that works out to roughly 3 gallons of compound, 120 ft of tape, and 400 screws.

Tips and common mistakes

  • Forgetting the ceiling. In the default room the ceiling adds 120 sq ft, more than either 12 ft wall (96 sq ft). Decide up front, because it may also need a different thickness.
  • Ignoring wall height. Two 4 ft rows cover an 8 ft wall exactly. At 9 ft you need a strip across the bottom or 54 in wide panels, and the offcuts add waste.
  • Counting on every window to save a sheet. The cutout from a small window is usually scrap. The 10 percent extra covers some of this, but round up in rooms with many openings.
  • Buying short sheets for long walls. Every place two sheet ends meet is a butt joint that is harder to finish flat. Match the sheet length to the wall where you can.
  • Not planning the route in. A 12 ft sheet has to make it through doors, around corners, and up stairs. Measure the path before you order long sheets.
  • Mixing up thicknesses. Keep ceiling board and wall board separate on the order if they differ, and use the thickness your code requires.

Frequently asked questions

How many sheets of drywall do I need for a 12 x 12 room?

With 8 ft walls, one door, and one window, a 12 x 12 room has about 349 sq ft of wall. Adding 10 percent for cuts brings it to about 384 sq ft, which is 12 sheets of 4 x 8 or 8 sheets of 4 x 12. Include the 144 sq ft ceiling and you need 17 sheets of 4 x 8.

How many square feet are in a sheet of drywall?

Multiply the width by the length. A 4 x 8 sheet is 32 sq ft, 4 x 10 is 40 sq ft, 4 x 12 is 48 sq ft, and a 4 x 16 sheet is 64 sq ft. USG also makes 54 in wide panels, which suit 9 ft walls hung in two rows.

Should I buy 4 x 8 or 4 x 12 drywall?

Longer sheets mean fewer seams to tape and fewer sheets to hang, so 4 x 12 panels make sense on walls longer than 8 ft. They are also heavier and harder to carry up stairs or fit through doors, so 4 x 8 sheets make sense for small rooms, tight spaces, and working alone.

What thickness of drywall should I use?

Under IRC Table R702.3.5, half-inch board meets the minimum for walls framed up to 24 in on center, and for ceilings up to 24 in on center when it runs perpendicular to the framing. If a ceiling will get a water-based texture, a footnote to the table requires at least 1/2 in board on 16 in framing, and 5/8 in or 1/2 in sag-resistant board on 24 in framing. Your local code has the final word.

How much joint compound and tape do I need?

USG estimates about 10 gallons of its all-purpose ready-mixed compound and about 370 ft of paper tape per 1,000 sq ft of board. For a 317 sq ft room, that is roughly 3 gallons of compound and 120 ft of tape.

Should I subtract windows and doors from a drywall estimate?

Our calculator subtracts about 20 sq ft per door and 15 sq ft per window, then adds 10 percent for cuts. Doors usually save real material. Small windows often do not, because the piece you cut out is usually scrap, so round up if your room has many small openings.