Room size in, full drywall order out — sheets, screws, joint compound, tape and corner bead, with the openings deducted and waste already added.
Openings
Most installers do not deduct — sheets are hung over openings and cut out afterwards, and the offcut is rarely reusable.
Materials
%
10% for a simple rectangular room, 15% where there are many corners, angles or alcoves.
Sheets to buy
—
Wall area—
Ceiling area—
Total area with waste—
Screws—
Joint compound—
Joint tape—
Corner bead—
Estimated material cost—
—
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How the quantities are worked out
Wall area = perimeter × ceiling height. For a 16 × 12 ft room the perimeter is 56 ft, so at 8 ft high that is 448 ft² of wall. Ceiling area = length × width, another 192 ft². Add waste, divide by the area of one sheet, round up.
Sheet size matters more than it looks
Longer sheets mean fewer butt joints, and butt joints are the hardest ones to hide because there is no tapered edge to bury the tape in. If a wall is 12 ft long, a single 4 × 12 sheet spans it with no butt joint at all. The trade-off is weight and handling — a 4 × 12 half-inch sheet is around 75 lb and awkward for one person, which is why 4 × 8 remains the default for DIY work.
The consumables
Item
Rule of thumb
Screws
32 per 4 × 8 sheet · about 320 screws per pound
Joint compound
Roughly 1 gallon per 100 ft² for tape plus three coats
Joint tape
About 40 ft per 100 ft² of drywall
Corner bead
Measured directly — one length per outside corner
Which thickness
½ in is standard for walls and for ceilings on 16 in centres. ⅝ in is required for garage ceilings, most fire-rated assemblies, and any ceiling framed at 24 in centres, where ½ in will sag between joists. Use moisture-resistant board in bathrooms and cement board behind tiled wet areas — regular drywall belongs in neither.
Always do the ceiling before the walls, so the wall sheets push up and support the ceiling edges. Hang wall sheets horizontally in residential work: it puts the tapered seam at a comfortable working height, crosses more studs for stiffness, and produces roughly 25% less joint length to finish than vertical hanging. Leave a small gap at the floor — the baseboard covers it, and board wicking moisture off a slab is a genuine problem.
Buy more mud than you think
Compound is the thing everyone runs short of, because it takes three coats and each one is sanded partly away. Ready-mixed all-purpose is the simplest choice for a first job; setting-type ("hot mud") sets chemically in 20 to 90 minutes rather than drying, which lets you do multiple coats in a day but gives you no time to fiddle. Many finishers use setting-type for the tape coat and ready-mix for the finish coats.
A spare sheet is worth having. Damaged corners, a mis-measured cut and patching are all normal, and a second trip for one sheet costs more in time than the sheet does.
Painting afterwards? The paint calculator works from the same wall areas — remember new drywall needs a primer coat that soaks in far more than the finish coats.
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Frequently asked questions
How many sheets of drywall do I need for a 12x16 room?
With 8 ft ceilings, walls are 448 ft² and the ceiling adds 192 ft², giving 640 ft². With 10% waste that is 704 ft², or 22 sheets of 4 × 8. Larger sheets reduce the count and, more usefully, the number of joints.
Should I deduct doors and windows?
Most installers do not. Sheets are hung straight over the opening and cut out afterwards, which gives cleaner edges and avoids joints landing at the corners of openings where cracks start. Deduct only if you are working to a tight budget on a wall with very large glazing.
How much joint compound do I need?
Roughly one gallon per 100 ft² of drywall for taping plus three finish coats. A 4.5 gallon bucket covers about 450 ft². Buy extra rather than less — running out mid-coat leaves a visible transition.
How many screws per sheet of drywall?
About 32 for a 4 × 8 sheet on 16 inch centres — every 12 inches in the field and every 8 inches along the edges. Ceilings get more, roughly every 7 inches. One pound holds around 320 screws.
What thickness of drywall should I use?
Half inch for standard walls and ceilings on 16 inch framing. Five-eighths for garage ceilings, fire-rated walls and any ceiling on 24 inch centres, where half inch sags. Moisture-resistant board for bathrooms, and cement board behind tile in wet areas.