Drywall Calculator

How to use this drywall calculator

1. Measure each room’s length and width along the floor, and the wall height from the floor to the ceiling. Feet and inches both work, or switch to metric.
2. Count the doors and windows. By default the calculator subtracts 20 square feet for each door and leaves windows in. You can change the rule under “Doors and windows” and the opening sizes in the settings.
3. Tick “Cover the ceiling too” if you’re hanging the ceiling. Ceiling sheets get their own line because many people buy a different board for overhead.
4. Pick a sheet size. Sheets of 4 × 8 are the easiest to carry. Sheets of 4 × 12 leave fewer seams to finish.
5. Add more rooms if you need to. The calculator adds them up before rounding, because offcuts from one room often finish another.

The result lists sheets, joint compound, paper tape, and screws. The cost uses example prices, so change them to match your store.

How the calculator works

The sheet count comes from area, then rounds up. The supplies come from the area you hang:

wall area      = 2 × (length + width) × height − 20 sq ft per door
ceiling area   = length × width
sheets         = area × 1.10 ÷ sheet area, rounded up
compound (gal) = (wall + ceiling area) × 10 ÷ 1,000
tape (ft)      = (wall + ceiling area) × 370 ÷ 1,000
screws         = wall sheets × 28 + ceiling sheets × 35   (4 × 8 sheets)

The 10% extra is our estimate. It pays for the short pieces left at the end of each wall, the cutouts around windows and outlets, and a corner that breaks off in the stairwell. Use 15% for rooms with lots of corners, short walls, or a sloped ceiling, or if this is your first drywall job.

Doors come off the total because a door removes a big, clean rectangle of wall. Windows stay in because the piece you cut out of a window is rarely usable. CertainTeed’s own calculator tells you not to subtract any openings, which is the “subtract nothing” choice. Pick “subtract doors and windows” for very large windows or sliding doors.

USG’s submittal sheets give the supply numbers: about 10 gallons of Sheetrock All Purpose ready-mixed compound and 370 feet of paper tape per 1,000 square feet of drywall. The compound comes in 4.5-gallon pails and 3.5-gallon cartons, and the tape in 250-foot and 500-foot rolls. The calculator picks the cheapest mix at your prices.

Screws are our estimate built from USG’s spacing for 1-1/4 inch screws: no more than 16 inches apart on walls and 12 inches apart on ceilings, with framing 16 inches on center. A 4 × 8 sheet hung horizontally crosses 7 studs or joists. That’s 4 screws per stud on a wall and 5 per joist on a ceiling. We convert to pounds at about 240 screws per pound, the count printed on a typical 1-pound box of #6 × 1-1/4 inch coarse-thread screws.

A worked example

Say you’re hanging a 12 × 14 bedroom with 8-foot walls, one door, and two windows, and you’re doing the ceiling too, with 4 × 8 sheets.

• Walls: 2 × (12 + 14) × 8 = 416 square feet, minus 20 for the door = 396 square feet
• Wall sheets: 396 × 1.10 ÷ 32 = 13.6, so 14 sheets
• Ceiling: 12 × 14 = 168 square feet, × 1.10 ÷ 32 = 5.8, so 6 sheets
• Joint compound: 564 square feet × 10 ÷ 1,000 = 5.6 gallons
• Tape: 564 × 370 ÷ 1,000 = 209 feet, so one 250-foot roll
• Screws: 14 × 28 + 6 × 35 = 602 screws, about 2.5 pounds

That’s 20 sheets in all. With 4 × 12 sheets the same room takes 10 for the walls and 4 for the ceiling. Fourteen sheets instead of twenty means fewer joints to tape, and both 12-foot walls go up with no end joint in the middle.

Drywall for common room sizes

Sheets for the walls and the ceiling, with 8-foot walls, one door subtracted, windows left in, and 10% extra:

Painting the new walls next? The paint calculator uses the same room measurements. Prime the fresh compound and paper first so the finish coats look even.

Tips for buying and hanging drywall

• Hang the ceiling first. The wall sheets then hold up the edges of the ceiling sheets.
• Run wall sheets horizontally. On an 8-foot wall that puts the long seam at about 4 feet, an easy height to tape and sand.
• Keep end joints off the same stud. Staggering them from row to row makes the seams far less likely to show.
• Use moisture-resistant board in bathrooms and laundry rooms. In a shower, tile goes over cement backer board, not drywall.
• Ask about delivery for 4 × 12 sheets. They won’t fit in most cars, and some stores will carry them into the room for a fee.