Drywall Calculator

Enter the room's length, width and wall height, pick your sheet size, and get the sheets to buy plus the joint compound, tape and screws, with every joint laid out on your own room so you can see what longer sheets would save.

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How the drywall calculator works

We start where every drywall estimate starts: the square feet of wall (the room's perimeter times its height) plus the ceiling if you are hanging one. Divide by the square feet in one sheet, round up, and you have the board. Then we do the part most calculators skip. We lay the sheets out on your actual room, four feet high and running sideways the way the USG handbook recommends, and count every foot of joint that has to be taped: the long tapered seams between courses, the butt joints where two sheet ends meet, and the inside corners. That count is your tape, and it is also the reason sheet size matters more than it looks.

Joint compound comes from USG's published coverage for its all-purpose compound, about 10 gallons for every 1,000 sq ft of board, and screws come from GA-216's fastener spacing (16 inches apart on walls, 12 inches on ceilings) laid over your sheet size and framing. Every number is shown with the arithmetic in the result, so you can follow it line by line.

The formula

sheets = [2 × (L + W) × H (+ L × W for a ceiling)] ÷ (4 × S), rounded up
tape = tapered seams + butt joints + inside corners
compound (gal) = 10 × board area ÷ 1,000
screws = (wall area × wall rate + ceiling area × ceiling rate) ÷ 1,000

L, W and H are the room's length, width and wall height in feet, and S is the sheet length (8, 10 or 12 ft). Tapered seams run along each course of sheets, so an 8 ft wall has one; butt joints number one fewer than the sheets in each course, staggered between courses as GA-216 requires. The screw rates are USG's published screws per 1,000 sq ft for your sheet, framing and spacing.

Worked example

A 15 by 12 ft bedroom with 8 ft walls, the ceiling included, one door and two windows, hung with 4 x 8 sheets on framing 16 inches apart. The walls are 2 × (15 + 12) × 8 = 432 sq ft and the ceiling 180 sq ft, so 612 sq ft. The door and windows (51 sq ft at our standard allowances) are figured solid: 612 ÷ 32 = 19.13, rounded up to 20 sheets.

Laid out, the walls take two courses, leaving 54 ft of tapered seams and 32 ft of butt joints. The ceiling runs its sheets along the 15 ft side in three courses: 30 ft of tapered seams and 12 ft of butt joints. Add 86 ft of inside corners and the tape comes to 214 ft, one 250 ft roll. The 561 sq ft of board that stays up needs about 5.6 gallons of compound (two 4.5 gallon pails) and about 580 screws.

Now hang the same room with 4 x 12 sheets: 13 sheets, and the tape drops to 198 ft. The butt joints go from 44 ft to 28 ft. And 4 x 10 sheets? Still 44 ft of butt joints, because a 12 ft wall and a 15 ft wall both need two 10 ft sheets in each course, exactly as they needed two 8s.

Bigger sheets, fewer seams, and where the saving actually lands

Here is the part that surprised us when we laid it out. On any room, the tapered seams depend only on how many courses the wall height takes, and the inside corners depend only on the room's shape. Sheet length changes exactly one thing: the butt joints. Those are the joints where two factory ends meet with no taper to hide the tape in, so they have to be feathered wide and are the ones that show under a raking light. So every foot of taping a longer sheet saves comes off the hardest joints in the room.

In the bedroom above, 4 x 12s cut the butt joints by 36 percent (44 ft down to 28 ft) while the total taping falls only 7 percent. In a 12 by 12 room, 4 x 12s remove every butt joint there is: 44 ft of them with 4 x 8s, none at all with 4 x 12s, and the taping falls from 196 ft to 152 ft. That is why the USG handbook says one board should span the entire length or width of a wall or ceiling if possible. The honest cost is weight: a half-inch lightweight 4 x 12 is about 60 lb against 40 lb for a 4 x 8, and it wants two people and a ladder plan. The sheet length that helps is the one that matches your walls, which is why the calculator shows all three on your room.

Why estimators do not subtract the windows

It feels wrong to buy board for a hole, but the USG handbook notes that estimators frequently figure door and window openings solid, subtracting only big ones like picture windows and wide patio doors. The reason is in how the board goes up. GA-216 keeps joints at least 12 inches from the corners of doors and windows, so a sheet is hung right across the opening and the hole is cut out of it afterward. That cutout is scrap. Figuring openings solid simply turns them into your waste allowance, and on the bedroom above it matches a sheet-by-sheet layout exactly: 20 sheets of 4 x 8, or 13 of 4 x 12. If you have large openings, switch to subtracting them and keep a waste allowance of about 10 percent, our editorial default.

Screws: why the ceiling gets more

GA-216 lets screws sit up to 16 inches apart on walls framed 16 inches on center, but only 12 inches apart on ceilings, where every screw is holding the board up against gravity rather than just holding it flat. On wider 24 inch framing it asks for 12 inches everywhere. On a 4 x 8 sheet laid across the framing, that works out to 28 screws on a wall and 35 on a ceiling with 16 inch spacing, which matches USG's published screw usage table exactly. The same standard sets minimum screw lengths: 1-1/8 inches for half-inch board and 1-1/4 inches for five-eighths.

The 370 feet rule, and the question it answers

USG's paper tape carries a handy rule: about 370 ft of tape per 1,000 sq ft of board. It is a good average for stocking a truck for a week of ordinary rooms, and on the bedroom above it says 208 ft against our layout count of 214. What it cannot see is your room. Taller walls add a whole course of seams (a 16 by 12 room with 9 ft walls, a door, a window and no new ceiling needs about 248 ft by layout with 4 x 8s, while the rule says 173), and longer sheets take butt joints away. For one room, counting the joints answers the better question. If you are planning the finish too, our paint calculator picks up where the mud leaves off.

Sources

Where the numbers on this page come from. We go to the body that publishes the figure, not to another calculator. See how we verify.

The Gypsum Construction Handbook, Chapter 3: Cladding, USG and CGC. Estimators frequently figure door and window openings solid, with large picture windows and large door openings the exceptions; one board should span the whole wall or ceiling if possible; perpendicular application reduces the lineal footage of joints up to 25%; 4 ft panels laid horizontally suit walls up to 8 ft 1 in, and 54 in panels walls from 8 ft 1 in to 9 ft 1 in.
The Gypsum Construction Handbook, Appendix: Gypsum Board Screw Usage, USG. Screws per 1,000 sq ft by board length, framing spacing and screw spacing, for horizontal attachment: 875 (walls) and 1,094 (ceilings) for 4 x 8 board on 16 in framing, 781 on 24 in framing, and the 4 x 10 and 4 x 12 columns. The page uses these figures directly and its tests rebuild every cell from the panel geometry.
GA-216, Application and Finishing of Gypsum Panel Products, Gypsum Association. Section 5.4 (2016 edition): screws no more than 12 in apart on ceilings and 16 in on walls where framing is 16 in on center, and 12 in on both where framing is 24 in on center. Also 4.6.4 (no joint within 12 in of the corner of an opening), 4.6.7 (end joints staggered between courses), and Table 5 (minimum screw length 1-1/8 in for 1/2 in board, 1-1/4 in for 5/8 in).
USG Sheetrock Brand All Purpose Joint Compound, submittal sheet J1969, USG. Coverage of approximately 10 gallons per 1,000 sq ft of gypsum panels, and the 4.5 gallon pail.
USG Sheetrock Brand Paper Joint Tape, submittal sheet J1736, USG. Coverage of approximately 370 ft of tape per 1,000 sq ft of gypsum panels, and the 75, 250 and 500 ft roll lengths.
USG Sheetrock Brand UltraLight Panels, submittal sheet WB2501, USG. Nominal weight of 1.25 lb per sq ft for 1/2 in lightweight panels, which gives the sheet weights in the comparison table, and panel lengths of 8 to 16 ft in 4 ft and 54 in widths.

Frequently asked questions

How do you calculate how much drywall you need?

Multiply the room's perimeter by the wall height, add the ceiling (length times width) if you are hanging it, and divide by the square feet in one sheet: 32 for a 4 x 8, 40 for a 4 x 10, and 48 for a 4 x 12. Round up. A 15 by 12 ft room with 8 ft walls and a ceiling is 612 sq ft, which is 20 sheets of 4 x 8. Professional estimators usually leave doors and windows in that area, because the cutouts come out of whole sheets and end up as scrap.

How many sheets of drywall do I need for a 12x12 room?

With 8 ft walls, the walls alone are 384 sq ft: 12 sheets of 4 x 8, or 8 sheets of 4 x 12. Add the 144 sq ft ceiling and it is 17 sheets of 4 x 8 (16.5, rounded up) or 11 sheets of 4 x 12. In that room the 4 x 12s also remove every butt joint, which cuts the taping from 196 ft to 152 ft.

Should I use 4x8 or 4x12 drywall?

Use the longest sheet that matches your walls and that you can handle. Sheet length only changes the butt joints, the hardest joints to finish: in a 15 by 12 bedroom, 4 x 12s cut them from 44 ft to 28 ft, and in a 12 by 12 room from 44 ft to none. The cost is weight and handling: a half-inch lightweight 4 x 12 is about 60 lb against 40 lb for a 4 x 8, and it needs two people and a clear path up the stairs.

How many screws do I need per sheet of drywall?

GA-216 spaces screws at most 16 in apart on walls framed 16 in on center and 12 in apart on ceilings. A 4 x 8 sheet hung sideways crosses 7 studs or joists, so it takes 28 screws on a wall and 35 on a ceiling. On 24 in framing both spacings drop to 12 in, and a sheet crosses 5 members for 25 screws. Those match USG's published screw usage of 875, 1,094 and 781 per 1,000 sq ft. Buy a little extra for the ones that hit the floor.

How much joint compound do I need for drywall?

USG rates its all-purpose ready-mixed compound at about 10 gallons per 1,000 sq ft of board, covering taping, filling and finishing coats. So a 4.5 gallon pail finishes about 450 sq ft, roughly 14 sheets of 4 x 8. A 15 by 12 bedroom with its ceiling, 561 sq ft of board once the openings are cut out, needs about 5.6 gallons: two pails.

How much drywall tape do I need?

Add up the tapered seams between courses of sheets, the butt joints where sheet ends meet, and every inside corner, including the line where the walls meet the ceiling. A 15 by 12 bedroom with 8 ft walls and a ceiling comes to 214 ft with 4 x 8 sheets, one 250 ft roll. USG's rule of thumb is about 370 ft per 1,000 sq ft of board, which makes a 500 ft roll good for about 1,350 sq ft.

Should I subtract doors and windows when estimating drywall?

Usually not. The USG handbook notes that estimators frequently figure openings solid, subtracting only large ones like picture windows and wide door openings. GA-216 keeps joints at least 12 in from the corners of an opening, so sheets are hung across doors and windows and the hole is cut out afterward, which makes the cutout scrap. Leaving openings in the area turns them into your waste allowance.

Should drywall be hung horizontally or vertically?

On walls up to 8 ft 1 in tall, hanging sheets horizontally, across the studs, is generally preferred. The USG handbook says it reduces the lineal footage of joints to be treated by up to 25 percent, runs the board's strongest direction across the framing, and puts the long seam at a comfortable height to finish. For walls from 8 ft 1 in to 9 ft 1 in, 54 in wide panels cover the height in two courses instead of three.