How Much Drywall Do I Need? Sheets, Waste and Screws

2026-10-23

To work out how much drywall you need, add up the area of every wall and ceiling you're covering, add a waste allowance (10% for a plain room), divide by the area of one sheet and round up. A standard 4×8 sheet covers 32 sq ft. A 12 × 14 ft room with 8 ft walls has 416 sq ft of wall and 168 sq ft of ceiling, 584 sq ft in total. That's 18.25 sheets of bare area, and 21 sheets to buy once you add 10% and round up.

The method fits on a sticky note, but the answers people get still vary. Guides quietly disagree in four places: whether to subtract doors and windows, when to round, how many screws a sheet takes, and how to get from a house's floor area to sheets of board. Here's each one, with numbers you can check.

How much drywall do I need for one room

Wall area is the room perimeter times the wall height, or (length + width) × 2 × height. Ceiling area is length × width. Georgia-Pacific's gypsum board guide uses exactly these two formulas. Its own example is a 12 × 16 ft room with 8 ft walls: 448 sq ft of wall and 192 sq ft of ceiling, 640 sq ft in all.

Then divide by the area of the sheet you plan to hang:

• 4×8: 32 sq ft
• 4×9: 36 sq ft
• 4×10: 40 sq ft
• 4×12: 48 sq ft

The same guide has a coverage table that shows the idea from the other side. A 20 × 12 ft ceiling is 240 sq ft, which is exactly five 4×12 sheets. A 16 × 10 ft ceiling is 160 sq ft, exactly four 4×10 sheets. Those are tidy cases with zero waste. Real rooms with corners, a door and a window rarely work out that neatly.

Should you subtract doors and windows?

This is where the top guides split. Inch Calculator tells you to subtract openings for a closer number. ProBuilderCalc says not to: the cut-outs get reused as filler pieces, and the waste allowance covers the rest.

Both approaches can work. The mistake is mixing them. If you don't subtract openings, you're already carrying spare board, and a full 10% waste on top of that is a second margin. If you do subtract, keep the waste allowance, because offcuts around a window rarely fit anywhere else.

Openings only ever come off the walls. In the 12 × 14 ft room, 40 sq ft of doors and windows brings the walls down from 416 to 376 sq ft, and the ceiling stays at 168. A sensible middle ground is to subtract large openings like patio doors and wide windows, and to ignore small ones if you'd rather have a little spare.

Waste, and the only rounding that matters

For waste, 10% is the usual figure for a plain rectangular room. Use 15% when there are lots of openings, angled walls or a vaulted ceiling. Russian state estimating norms, which are written for contractors' cost estimates, come out at 105 sq m of board per 100 sq m of blank wall and 111 per 100 sq m of suspended ceiling. Even in contractors' own norms, ceilings waste more than walls.

Apply the waste to the total area and round once, at the very end. For the 12 × 14 room, 584 sq ft becomes 642.4 sq ft with waste, and that divides into 21 sheets. If you round up each wall separately and then add 10% on top, you stack two margins and end up with sheets you'll return.

Keep in mind what the area method assumes: that offcuts from one wall get used on another. In a room full of short pieces, soffits and returns, that assumption breaks first. Raising the waste percentage is the honest fix. Fiddling with individual wall counts isn't.

When the wall is taller than the sheet

The area math also assumes your sheets actually fit the walls. With 8 ft walls they do. A 4×8 sheet runs floor to ceiling standing up, and two 4 ft rows laid horizontally make exactly 8 ft.

At 9 ft walls, 4×8 sheets leave a 1 ft gap along every wall. The area total still counts that strip, but in practice it comes from cutting into full sheets, and it adds an extra horizontal joint to tape on every wall. That's why 4×9 sheets exist. Manufacturers make 4 ft wide board in lengths from 8 to 16 ft, so match the sheet to the height first and then count.

Longer sheets also mean fewer butt joints to tape. The catch is weight: a 1/2 inch 4×8 sheet is about 54 lb and a 4×12 is about 82 lb. That's a two-person lift, and a ceiling is harder still.

How many screws per sheet of drywall

Two figures circulate. One is about one screw per square foot, roughly 32 per 4×8 sheet, which gives about 600 screws for the 12 × 14 room. The other comes from Georgia-Pacific's estimating table: 1,250 screws per 1,000 sq ft of board. For the same room that's 730.

The manufacturer's figure is about a quarter higher. Screws are cheap and running out halfway through a ceiling isn't, so buy to the higher number. Fire-rated and two-layer assemblies are a separate case. They follow the fastener spacing in their tested listing, not a rule of thumb.

What about a whole house?

Half of Google's suggestions for "how much drywall do I need" end in something like "for a 1500 sq ft house". There's no honest single answer, because floor area isn't board area. In Georgia-Pacific's 12 × 16 ft example, 192 sq ft of floor needs 640 sq ft of walls and ceiling, more than three times as much.

That multiplier also changes with room size. Georgia-Pacific's room table, at 8 ft walls, gives:

• 8 × 8 ft room: 64 sq ft of floor, 320 sq ft of board, five times the floor;
• 16 × 16 ft room: 256 sq ft of floor, 768 sq ft of board, three times the floor.

Small rooms have far more wall per square foot of floor. Interior walls are covered on both sides, closets and hallways add wall but little floor, and taller ceilings scale everything up. A house built from bedrooms and hallways needs a lot more board per square foot than an open-plan one. Measure room by room, or have a supplier take quantities off the plans.

What to put in the calculator

The drywall calculator does all of the above in one pass. Enter:

• what you're covering: one wall, all walls, the ceiling, or walls and ceiling;
• the room length and width, and the wall height;
• the total area of doors and windows, if you want them subtracted;
• the sheet size and the waste percentage.

It returns the sheets to buy, the net area and the area with waste, and the screw count. It also works in metric with 1200 mm sheets, where it adds the metal frame for wall lining and suspended ceilings. It's an area-based estimate rather than a sheet layout, so it doesn't cover partitions, double layers or joint compound. Once the board is up and finished, the paint calculator and the wallpaper calculator use the same wall measurements for the next step.