Drywall Calculator

Drywall is sold as flat sheets, not by the square foot, so the calculator converts area into sheets. It offers 4x8, 4x10 and 4x12 ft sheets, and longer sheets cover more wall with each piece.

How to use this calculator

1. Measure the room's length and width in feet at floor level, and the wall height from the floor to the ceiling. For an L-shaped room, measure each section as a rectangle and add the results. Walls shared between sections get counted in both, which errs toward more board.
2. Leave the ceiling option on if the ceiling will be boarded too. Set it to no for a wall-only job.
3. Choose the sheet size. Longer sheets need fewer seams, but they are heavier to carry through a doorway, so check the route first.
4. Open More options to enter the area of any doors and windows you want to subtract, and check the extra for waste. The default is 12 percent, so raise it for a room with many corners or openings.
5. Work out the joint compound and tape with the joint compound and tape calculator. They are a separate purchase from the board.

Worked examples

Drywall sheets for common room sizes, with the ceiling included

Each cell: Drywall sheets (sheets). Inputs not in the table use the calculator's starting values.

What the sheet count is built from

The calculator multiplies the room's perimeter by the wall height and subtracts any openings to get the wall area. A ceiling adds the floor area. It then adds the extra for waste, divides by the area of a sheet and rounds up, because a store will not sell part of a sheet.

The default extra, 12 percent, comes from a state environmental agency's figure for drywall wasted during installation in new construction, not from a board maker. Manufacturers' own estimators leave waste out, so this default adds a margin they do not. Treat it as a starting point.

Screws are estimated from the wall and ceiling area before waste, using the maker's handbook figure of 850 to 1,000 screws per 1,000 sq ft for wood framing. The calculator uses the top of that range. For metal studs, check the screw type with the framing maker.

Sheet length, seams and openings

Each sheet edge that meets another sheet is a seam, and each seam needs tape and joint compound. Longer sheets cover more wall between seams, so a room has fewer to finish, though each sheet is heavier to handle.

Many installers hang full sheets over doors and windows and cut the openings out afterward, which saves measuring every opening exactly. That makes subtracting openings optional. If you subtract them, keep the extra for waste on, because a bad cut can ruin a sheet.

Fire-rated and moisture-resistant board

Local codes may require fire-rated or moisture-resistant board in certain rooms, and the rules depend on the location. Check with your building department before you order. The calculator counts every board the same, so confirm that the board you pick comes in the sheet size you chose.

Moisture-resistant board is often used in damp rooms such as bathrooms. Showers and other wet areas usually call for a backer board made for tile, so follow the tile maker's instructions, and work out the tile count with the tile calculator.

Mistakes to avoid

• Ordering exactly the wall area in sheets. Cuts and offcuts at corners need extra board, so keep the default extra or raise it.
• Leaving the ceiling in when it stays out, or out when it will be boarded. Check the ceiling option before you read the sheet count.
• Picking a sheet size without checking the walls. A long sheet that overshoots a short wall leaves an offcut that may not fit anywhere.

What thickness of drywall should I use?

Common thicknesses are 0.5 inch and 0.625 inch. The thicker board is the safer pick for ceilings and wide framing spacing, and it is used for fire-rated walls. Check the model code table for your framing spacing and your local rules before you order, and make sure that thickness comes in your sheet size.

Common questions