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

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.

Drywall sizes for walls: 8, 9, 10, and 12 ft walls

2 rows of 48 in sheets cover an 8 ft wall with one seam, and 2 rows of 54 in sheets do the same on a 9 ft wall. USG makes its UltraLight and Firecode X panels 48 or 54 in wide and 8 to 16 ft long, so on a taller wall you either add a strip or stand the sheets on end:

The last column is the calculator's own count for a 12 x 12 room with one door, one window, and 10 percent extra; enter your wall height and it scales the same way. The calculator assumes 4 ft wide sheets. For 54 in panels, divide the area with extra by 4.5 times the sheet length: the 12 x 12 room with 9 ft walls comes to about 437 sq ft with extra, and 437 / 54 = 8.1, so 9 sheets of 54 in x 12 ft. Check which lengths your supplier stocks, and round up on walls that need a strip, since the rest of the cut sheet is often scrap.

Drywall sheets by room size

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

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. Plywood and OSB come in the same 4 x 8 size; the plywood calculator counts those sheets.

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.

Drywall weight per sheet by type

40 lb for a 4 x 8 sheet of USG's lightweight 1/2 in UltraLight and 70 lb for a 4 x 8 sheet of its 5/8 in Firecode X. Type X is the heaviest board in the table. The weights below are each manufacturer's nominal weight per square foot times the sheet area, rounded to the pound:

USG's UltraLight Firecode X is about 14 percent lighter than its standard Firecode X, and USG says it offers comparable sound, strength, and sag resistance to standard 5/8 in Type X. Gold Bond says tests show its 1/2 in High Strength LITE board equals 5/8 in Type X in sag resistance. USG gives its weights as approximate, for design and shipping, so check the label on the board you buy.

Drywall sizes chart by thickness

Drywall also comes in several thicknesses, each with its own uses. The widths, lengths, and uses below are from USG's data sheets for its regular 1/4 and 3/8 in panels, its lightweight 1/2 in UltraLight panels, and its 5/8 in Firecode X panels. Sheet weights are worked out from USG's nominal weight per square foot.

National Gypsum adds that its 1/4 in board can be hung in double layers to form curved surfaces with short radii. The minimum thickness for your walls and ceilings comes from the code; see the next section.

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:

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.

Which drywall to use: walls, ceilings, garage, and bathroom

1/2 in board meets the IRC minimum for walls and ceilings framed up to 24 in on center; on 24 in ceiling framing it must run across the joists, and be sag-resistant under a water-based texture. Garages, the space under stairs, and tiled tub and shower walls have their own rules:

Type X is the fire-rated core: USG makes its Firecode X and UltraLight Firecode X panels for walls and ceilings where 5/8 in Type X is required, and Lowe's buying guide recommends Type X fire-resistant drywall for garages, stairwells, and areas near furnaces. The garage rows follow the 2018 IRC as summarized by the City of West Point, Georgia, and the stair row the 2015 IRC as summarized by the City of Grinnell, Iowa. The Gypsum Association notes that standard wallboard and greenboard are not permitted as a tile substrate in tub and shower areas. Your local code may differ.

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. Once the walls are finished, the paint calculator takes the same room length, width, and height.

Drywall mud and tape by room size

USG's figures of about 10 gallons of all-purpose compound and 370 ft of paper tape per 1,000 sq ft of board, applied to the surfaces in the sheet chart above: 8 ft walls, one door, one window, and no extra.

Drywall screws, mud, and tape per sheet

28 screws hold a 4 x 8 sheet on a wall framed 16 in on center at the widest spacing allowed. The Gypsum Association's GA-216 limits screw spacing to 16 in on walls and 12 in on ceilings when the framing is 16 in on center, to 12 in on both when it is 24 in on center, and keeps screws at least 3/8 in from edges and ends. That is one row of screws on every stud or joist the sheet crosses, ends included. Compound and tape use USG's figures of about 10 gallons and 370 ft per 1,000 sq ft:

The screw counts are minimums, since the spacing is a maximum. The CGC Gypsum Construction Handbook estimates about 1,000 screws per 1,000 sq ft for a single layer on walls framed 16 in on center and about 850 at 24 in, and Lowe's estimator plans 1,250 per 1,000 sq ft, or 40 per 4 x 8 sheet. A 4.5 gallon pail of USG all-purpose compound covers about 450 sq ft, or 14 sheets of 4 x 8.

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.