Drywall Calculator

Multiply the area by the number of sides you are covering, add an overage allowance, then divide by the sheet coverage and round up. A 4 by 8 sheet is 32 sq ft; a 4 by 12 is 48 sq ft; the less common 4 by 10 is 40. For 200 sq ft on one side with 10% overage, that is 220 ÷ 32 ≈ 7 sheets. The sides question is the one people forget. A new partition wall gets board on both faces, so a 200 sq ft wall is 400 sq ft of drywall. A ceiling, or an existing wall you are refacing, is one side. Framing a closet inside a room means the closet interior is one side and the room side is another — walk the job and count faces, not walls. For the area itself, walls come from perimeter × ceiling height and ceilings from the floor area. Whether to deduct doors and windows is a judgment call: on a wall with one door the deduction is small and it quietly becomes margin, but on a wall that is mostly glass, deducting is the difference between one sheet and three.

The choice between 4 by 8 and 4 by 12 looks like a question about cost per square foot. It is really a question about how much taping and sanding you want to do. Drywall has two kinds of seam. A tapered joint happens where the factory-thinned long edges of two sheets meet, leaving a shallow recess that swallows tape and compound and finishes nearly flat. A butt joint happens where two cut ends meet, with no recess at all — the tape and mud have to be feathered out wide over the surrounding board to hide a bump. Butt joints are the hard part of drywall finishing, and they are the ones that show up in raking light on a badly finished wall. Longer sheets exist to eliminate butt joints. On a 12 ft wall, one 4 by 12 sheet run horizontally reaches wall to wall with none; two 4 by 8 sheets create one. Fewer butt joints means less compound, less sanding and a better-looking wall. The cost is handling. A 4 by 12 sheet of half-inch board is on the order of 75 pounds and awkward for one person in a stairwell or a tight hallway; a 5/8 in sheet the same size is heavier still. Weights vary by manufacturer and by whether the board is a lightweight formulation, so check the product. If you are working alone, the smaller sheet you can actually control beats the larger sheet you drop.

Board is the headline item, and the rest of the list is what actually consumes the afternoon. Screws: roughly 32 per 4 by 8 sheet is a reasonable planning number, with spacing along each framing member. Ceilings take more fasteners than walls, and required spacing depends on the assembly and the code, so treat the number as an estimate for buying a box rather than an installation instruction. Screw length has to suit the board thickness and whether the framing is wood or steel. Tape for every seam and every inside corner, in paper or fiberglass mesh — different products want different compounds behind them. Joint compound, which is where the volume hides. A full three-coat finish is commonly quoted at somewhere around a gallon per 100 to 150 sq ft of board, but it depends heavily on how many butt joints you created and how heavy-handed you are. Setting-type compound and all-purpose compound behave differently and are often used at different stages. Plus corner bead on every outside corner, and if you are matching an existing surface, whatever texture the rest of the house has. A perfectly flat new patch next to a knockdown ceiling is a visible repair. One more consumable: sanding drywall compound generates a great deal of fine dust, and it travels through an entire house. Some joint compounds contain crystalline silica, so ventilate, use a dust mask suited to the work, and consider wet sanding or a vacuum sander for anything more than a small patch.

"Drywall" names a family of boards that look nearly identical stacked at the store and are not substitutes for each other. On thickness: 1/2 in is the general-purpose wall board. Ceilings are a special case, because gravity works on a horizontal sheet all day — 5/8 in, or a 1/2 in board specifically sold as sag-resistant ceiling board, is used to keep ceilings from sagging between joists, especially where the framing is spaced wider or the board will be sprayed with wet texture. Thin 1/4 in and 3/8 in boards exist for resurfacing over existing walls and for bending around curves. On type: standard board handles dry rooms. Moisture-resistant board, often green-faced, is intended for damp areas such as bathroom walls outside the direct spray zone. Cement board or an equivalent tile backer belongs behind tile in showers and tub surrounds, because paper-faced gypsum board is the wrong substrate for a wet wall no matter what color the paper is. Fire-rated board, commonly designated Type X, is required by code in specific assemblies — garages, walls shared with an attached dwelling, and around certain equipment. Which board goes where in your house is set by your local building code, and fire-rated assemblies in particular are code-driven and inspected. Do not substitute a board type to save a trip. If the wall is part of a rated assembly, the whole assembly — board type, thickness, fastener pattern and joint treatment — is specified together, and changing one part invalidates it.

Drywall wastes less than tile or flooring, because the offcuts are usable: the piece cut off the end of a wall sheet often becomes the panel above a door or beside a window. That is why a 10% allowance is generous for a simple rectangular room and why professional estimates on a plain job can run tighter. What the allowance really covers is damage. Gypsum board has fragile corners, breaks if flexed the wrong way, and does not survive being dropped on a stair nosing. It also absorbs water — a sheet left leaning outdoors overnight in the rain is scrap. Buy the extra sheet, and store the stack flat and dry. A little layout thought saves more than the allowance does. Running sheets horizontally on an 8 ft wall places the long tapered seam at a comfortable working height and produces one long tapered joint instead of several vertical butt joints. Stagger the joints between rows and between the two faces of a partition, and try not to land a seam at the corner of a door opening, where the framing moves most and cracks start. Finally, older homes. Houses built before 1978 may have lead-based paint on existing walls, and cutting into, sanding or demolishing those surfaces releases lead dust. Renovation work of that kind is covered by the EPA's Renovation, Repair and Painting rule. Find out what you are cutting into before the utility knife comes out — and check for wiring, plumbing and gas lines in the cavity while you are at it, since anything electrical or gas-related behind that wall is work for a licensed professional.