Drywall Calculator

Tip: longer sheets mean fewer seams to tape. If you can get 12 ft sheets into the room, an 8 ft tall wall can be hung with two horizontal rows and almost no butt joints.

Worked example

A 12 ft by 12 ft bedroom has 8 ft walls, one door and two windows, and you are hanging the ceiling too. The walls are 2 x (12 + 12) x 8 = 384 square feet and the ceiling adds 144.

Subtracting 21 square feet for the door and 15 for each window leaves 477 square feet to cover. With 10% extra for cuts, 477 x 1.1 = 524.7 square feet. A 4 x 8 sheet covers 32 square feet, so you need 524.7 / 32 = 16.4, which rounds up to 17 sheets.

Finishing that area takes about 4.5 gallons of all-purpose joint compound, about 177 ft of paper tape and roughly 500 drywall screws.

How to calculate drywall sheets

Add up the area of every surface you will cover. For walls, the perimeter of the room times the wall height gives the total wall area. For the ceiling, multiply length by width. Subtract openings: a standard interior door is about 21 square feet and an average window about 15. Then add an allowance for cuts and divide by the area of one sheet.

Round up to whole sheets. Pieces cut out for windows and doors are often usable above and below the openings, which is why a 10% allowance usually covers a simple room.

Choosing a sheet size

• 4 x 8 ft (32 sq ft): easiest to carry and fit through doors. About 55 pounds for 1/2 inch board.
• 4 x 10 ft (40 sq ft): good for 10 ft ceilings hung vertically, or longer walls.
• 4 x 12 ft (48 sq ft): fewest seams on long walls and ceilings, but heavy and awkward. Best with two people and a drywall lift for ceilings.

Thickness matters too. 1/2 inch is standard for walls. Ceilings often use 1/2 inch sag-resistant or 5/8 inch board, and garages and walls next to them usually need 5/8 inch Type X fire-rated board by code. Use moisture-resistant board in bathrooms.

Joint compound, tape and screws

For taping and two finish coats, plan on about 9.5 gallons of ready-mixed all-purpose compound per 1,000 square feet of board. That is roughly one 4.5 gallon bucket for a typical bedroom. Lightweight compound goes a little further. Paper tape runs about 370 ft per 1,000 square feet, and inside corners can use paper or metal-reinforced tape. Outside corners need corner bead.

Screws are typically placed every 12 inches on ceilings and every 16 inches on walls. About one screw per square foot of board is a good estimate. 1-1/4 inch coarse-thread screws are standard for 1/2 inch board on wood studs. Use fine-thread screws for metal studs.

Hanging tips that save material

Hang the ceiling first, then the walls, so the wall sheets support the ceiling edges. On walls, hanging sheets horizontally usually means fewer linear feet of joints and a stronger wall. Keep butt joints, the short ends that are not tapered, away from the middle of walls where they are hardest to hide, and stagger them between rows.

Do not piece together scraps to save a sheet. Every extra seam costs more time in mud and sanding than the board is worth.

Rooms that are not rectangles

For closets, L-shaped rooms and stairwells, measure each wall separately: width times height. Add them up, add the ceiling areas, subtract openings and divide by the sheet area. Vaulted ceilings are larger than the floor below them, so measure along the slope, or multiply the floor area by a pitch factor from the roofing calculator.

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Results are estimates, not a contractor quote. Check quantities with your supplier before you order, and follow local building codes.