Free tool
Drywall calculator
Work out how many sheets of drywall you need for walls or a ceiling, from the square footage and your sheet size, with waste built in. Feet and inches, free, no sign-up.
Measures all four walls plus the ceiling. Openings are not deducted, because you cut them out of full sheets.
- Area to cover
- 584 sq ft
- Each sheet covers
- 32 sq ft
- Joint compound
- 5.3 gal, 2 buckets
- Joint tape
- 217 ft, 1 roll
- Screws, 1-1/4 in
- 630
Sheets include a 10% waste allowance for cuts around doors, windows and outlets. Consumables are typical figures for a taped, three-coat finish: about 0.9 gallons of ready-mix compound and 37 feet of tape per 100 square feet of board, and roughly one screw per square foot on walls with framing 16 inches on center, a quarter more on a ceiling. Buckets are 4.5 gallons, tape rolls 250 feet. Figures update as you type.
Drywall is cheap and heavy, which is the worst combination for guessing. Order two sheets short and you lose an afternoon to a supply run and end up with a butt joint in the middle of a wall you did not want one on. This calculator works out the square footage of a room, the sheets for the size you are buying, and the mud, tape and screws to go with them. Here is how the numbers are worked out.
How to work out how many sheets of drywall you need
Work out the square footage, add waste for the cuts, then divide by the area of one sheet.
Sheets = square footage × (1 + waste) ÷ sheet area.
Walls are the perimeter times the ceiling height: a 14 by 12 foot room has 52 feet of perimeter, which at 8 feet high is 416 square feet. The ceiling is 14 × 12 = 168 square feet. That is 584 square feet in total, or 21 sheets of 4 by 8 once 10% waste is added. The calculator does the whole thing from three measurements.
Drywall sheet sizes
Every sheet is 4 feet wide, so the only thing that changes is the length.
- 4 by 8 covers 32 square feet. One person can carry it, and it fits in a pickup.
- 4 by 10 covers 40 square feet. Good for a 10 foot wall hung vertically.
- 4 by 12 covers 48 square feet, and hung horizontally it takes a 12 foot wall in one piece with no butt joints at all.
Longer sheets mean fewer seams to tape, which is where the labor is. They also mean two people and a clear path through the house, so pick the longest sheet you can actually get into the room.
Half inch or five eighths?
Half inch is the standard for walls and most ceilings. Five eighths goes where a fire rating is called for, on garage ceilings under living space, and on ceilings where the framing is 24 inches on center, because half inch sags between joists at that spacing. Five eighths is also stiffer and flatter across a long wall, which is why a lot of finishers prefer it.
The thickness sets the screw length: 1-1/4 inch screws for half inch board, 1-5/8 inch for five eighths. The calculator switches the screw length with the thickness you pick.
How much mud, tape and screws
These are the typical estimating figures for a taped, three-coat finish, and the ones the calculator uses.
- Joint compound: about 0.9 gallons of ready-mix per 100 square feet of board, so a 4.5 gallon bucket does around 500 square feet. Hand taping with a lot of butt joints runs closer to half a gallon a sheet, so buy an extra bucket if you are new to it.
- Joint tape: about 37 feet per 100 square feet of board, which is roughly 370 feet per 1,000. Standard rolls are 250 or 500 feet.
- Screws: roughly one per square foot on walls, which works out at about 32 in a 4 by 8 sheet with framing 16 inches on center. Ceilings take a tighter pattern, so allow about a quarter more.
Screw spacing is what those counts come from: 16 inches apart in the field of a wall and 8 inches around the perimeter, tightened to 12 inches in the field on a ceiling. Keep them at least 3/8 inch in from the edge so the screw does not blow out the gypsum core.
Hanging it so there is less to tape
Ceilings go up first, then the walls hold the ceiling edges tight. Hang wall sheets horizontally, across the studs, so the tapered seam runs level at about waist height instead of vertically every 4 feet. Fewer seams and no butt joints in the middle of a wall is the difference between a day of finishing and three.
How much waste to allow
Around 10% covers the cuts around doors, windows, outlets and corners, and the offcuts too small to use. Do not deduct openings from your square footage: you cut a window out of a full sheet and what falls out is mostly waste. A plain rectangular room with one door wastes less; a room with several windows, a stairwell or an odd shape wastes more, so push the allowance up for those.
What comes after hanging
Hanging is the fast part. Then it is tape, three coats of mud with a sand between, a prime coat and paint. Work out the paint for the finished room with our paint calculator, which handles the coats and the coverage.
Working in meters instead?
If you buy board by the sheet in millimetres, use the plasterboard calculator, which takes meters and millimetre sheet sizes.
From materials to a priced job
Sheets are one line on the quote. The labor in hanging, taping and finishing is most of the money, and the part people underprice. Price the whole job with how to price a job so you actually make a profit, and put the materials into a clean, itemized quote with the quote generator.
This tool is for general estimating and gives approximate quantities. Compound coverage, finish levels and room shapes vary, so check your own measurements and the coverage on the product, and order a sensible amount over rather than exactly to the calculation.
How do I work out how many sheets of drywall I need?
Work out the square footage, divide by the area of one sheet, and add waste. A 4 by 8 sheet covers 32 square feet, so a 400 square foot wall takes 13 sheets bare, or 14 once 10% is added. This calculator does it from the room and sheet sizes and rounds up to whole sheets.
What size sheets of drywall should I buy?
4 by 8 is the standard and the easiest to handle single-handed. 4 by 12 gives you fewer butt joints on a long wall and less taping, if you can get it into the room and have a second pair of hands. Half inch is normal for walls, and 5/8 Type X goes on ceilings, garages and anywhere with a fire rating.
How much waste should I allow for drywall?
Around 10% for a straightforward room. Push it to 15% where there are lots of openings, angles or short walls, because the offcuts come out too small to use anywhere else.
Do I deduct doors and windows?
Usually not for the small ones. Most hangers board straight over a door or window and cut the opening out after, so that piece is waste anyway. Deduct the big openings, a garage door or a wall of glass, and drop the waste allowance to match.
How many screws and how much joint compound will I need?
As a rough guide, figure about 32 screws to a 4 by 8 sheet on walls, a 4.5 gallon bucket of all-purpose compound for every 1,000 square feet across all coats, and a 500 foot roll of paper tape over roughly the same area. Coverage varies with how you finish, so check the bucket and buy a little over.
What is the difference between drywall and plasterboard?
Nothing but the name and the sizes. Drywall, sheetrock and wallboard in the US are the same product the UK, Ireland and Australia call plasterboard. US sheets come in feet, 4 by 8 or 4 by 12; metric sheets come as 1200 by 2400mm. Working in metric? Use the plasterboard calculator instead.
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