Calculators
Drywall sheet calculators
How many sheets a room, a ceiling, a basement or a garage takes, which size to buy, and where moisture-resistant or fire-rated board belongs.
A sheet count is not square feet divided by 32. It is the net area of each surface after the openings come out, the size and orientation of the sheet you can actually get into the room, and a waste allowance that depends on how many cuts the room forces. These calculators do those three steps in the open: every one of them prints the net area, the sheets before waste and the sheets after it, so you can see where the number came from and change what does not match your job.
They share the same conventions. Doors and windows are subtracted at their rough sizes, sheets are rounded up to whole pieces, and the fastener and compound summaries use the same spacing and coverage figures as the dedicated screw and joint compound calculators, so a shopping list built from several of these tools adds up.
9 calculators
Drywall Sheet Calculator
Sheets for the walls and ceiling of a room from its dimensions, openings, sheet size and waste, with the screws and compound to go with them.
Ceiling Drywall Calculator
Sheets for a ceiling from its length and width, with the thickness your joist spacing needs and the sheet direction.
Single Wall Drywall Calculator
Sheets, joints and butt joints for one wall, hung horizontally or vertically, with its openings taken out.
Basement Drywall Calculator
Sheets for up to six basement rooms at once, walls and ceilings, with a per-room breakdown and one shopping list.
Garage Drywall Calculator
Sheets for a garage by type: 5/8 in type X where the fire-separation rules require it and regular board elsewhere.
Sheet Size Optimizer
Every sheet length on one wall: sheets, butt joints, feet of joint and waste for each, and which one to buy.
Moisture-Resistant Board Calculator
Moisture-resistant board for a bathroom, kitchen or laundry, with the tub and shower area taken out for cement board.
Fire-Rated Drywall Calculator
Sheets of 5/8 in type X per layer and per side for a one- or two-hour wall or ceiling, with the screws for each layer.
Curved Wall Drywall Calculator
Board for a curved wall from its radius and angle: layers of 1/4 in or flexible board, the bending limits, stud spacing and screws.
Guides for this topic
Bathroom and kitchen drywall: where moisture board goes, and where not
Green board is for splash and steam, not for water. Knowing where the line falls between gypsum and tile backer is most of what there is to bathroom drywall.
4×8, 4×12 and the rest: sheet sizes, orientation and seams
The size and direction of the sheets decide how many joints there are to tape, and joints are where the labour and the visible flaws are. Here is how to choose.
Drywall thickness: 1/4, 3/8, 1/2, 5/8 and type X
Half-inch board covers most walls in most homes. The exceptions are ceilings on wide framing, fire separations, curves and sound walls, and each has a rule.
What drywall weighs and how to get it into the house
A room's worth of drywall weighs as much as a small car. Planning how it travels, where it is stacked and how it goes up saves backs, floors and corners.
Fire-rated drywall assemblies: what a rating means, where it is needed
A fire rating belongs to a whole wall, tested in a furnace, not to the board on it. Here is how ratings work and how to build to one.
Garage drywall: the fire-separation rules and type X
An attached garage is the one place most houses need fire-rated drywall. The rules are short and specific, and they decide which board goes on which surface.
Hanging drywall: ceilings first, then walls, and why
Every hanger does the ceiling first. The reason is structural, not habit, and the same logic decides the order of every row on the walls.
How many sheets of drywall do I need? The complete method
Square feet divided by 32 is where most counts start and where most go wrong. Here is the method a careful estimator follows, step by step, on a real room.
Questions people ask
- How many sheets of drywall do I need for a 12 by 12 room?
- With 8 ft ceilings, one door and one window, the four walls come to 349 sq ft net and the ceiling adds 144 sq ft. With 10% waste that is 17 sheets of 4 × 8 for walls and ceiling, or 12 sheets for the walls alone. Twelve-foot sheets bring the whole room to 12 sheets with far fewer butt joints.
- Should I buy 4 × 8 or 4 × 12 sheets?
- Buy the longest sheet you can carry into the room and lift into place. A 12 ft sheet hung horizontally spans a 12 ft wall with no butt joint, which saves tape, compound and sanding. For a room with 8 ft walls and 12 ft runs, 4 × 12 sheets usually cut the butt joints by two thirds. If the stairs or doorway will not take a 12 ft sheet, 4 × 8 is the practical answer.
- How do I work out drywall for a ceiling?
- Multiply the ceiling length by its width, add 10% for waste, and divide by the sheet area. Hang sheets perpendicular to the joists, and use 5/8 in board or 1/2 in sag-resistant ceiling board when joists are 24 in apart, because regular 1/2 in board, though allowed, sags more at that spacing. The ceiling calculator checks the joist spacing for you.
- Does an attached garage need 5/8 in type X drywall?
- In the International Residential Code (R302.6) the wall between the garage and the house needs at least 1/2 in gypsum board on the garage side, and a garage ceiling with living space above it needs 5/8 in type X. Local codes can be stricter, so check with your building department before buying.
- Where should I use moisture-resistant drywall?
- On bathroom, kitchen and laundry walls that get splashed or steamy but not soaked. Inside a tub or shower surround, where tile is set directly on the wall, codes call for cement board or another water-resistant tile backer rather than moisture-resistant gypsum. The moisture-resistant board calculator separates the two areas.
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