Plasterboard is sold by the sheet, and the standard sheet is 2400 by 1200 millimetres — exactly 2.88 square metres. Smaller formats are common where access is tight or where one person is boarding alone. A 1200 by 900 millimetre sheet is only 1.08 square metres and weighs about a quarter of a full sheet, which makes a ceiling possible without a board lifter. The sheet size you choose is therefore a handling decision before it is a quantity one.
Sheet size is not just a handling question, it is a waste question. A large sheet covers more per cut but leaves bigger offcuts, and boarding a 2.4 metre high wall with 2400 millimetre sheets stood on end wastes almost nothing, while the same wall in 1200 by 900 sheets creates a grid of joints that all have to be taped. Choose the sheet, then count.
A wall 4 metres by 2.4 metres with 1.8 square metres of openings is 7.80 square metres net, which is 2.71 standard sheets. That rounds up to 3 whole sheets, and 3 once a ten per cent allowance is added for cuts. Screws go in at roughly 300 millimetre centres, about thirty per full sheet, and each sheet contributes roughly its own length in jointing tape once shared joints are counted.
The formula
area- Length × height of the wall or ceiling in m²
openings- Doors, windows and hatches to deduct, in m²
layers- One normally, two for acoustic or fire upgrades
sheet area- 2.88 m² for a 2400 × 1200 sheet, 1.08 m² for 1200 × 900
How it works, step by step
- Enter the length and height of the wall, or the ceiling dimensions.
- Deduct the area of any doors, windows or hatches.
- Choose your sheet size and how many layers of board you are fixing.
- The gauge shows bare sheets; sheets to order, screws and tape follow.
Worked examples
A 4 × 2.4 m wall with a doorway
9.6 m² less 1.8 m² of opening is 7.80 m² net. At 2.88 m² per sheet that is 2.71, so 3 sheets bare and 3 with a 10% allowance, needing about 90 screws.
Small boards for a ceiling worked alone
The same 7.80 m² in 1200 × 900 sheets of 1.08 m² each needs 8 sheets rather than 3, and the jointing tape rises from about 7 m to 10 m. Easier to lift, much more filling.
How to read your score
Frequently asked questions
Which way should the boards run?
On a wall, whichever direction produces fewest joints — usually horizontally on a 2.4 metre high wall if the studs allow it, or vertically if the sheet height exactly matches the wall. On a ceiling, run the long edge across the joists so every board is supported at multiple points.
How many screws does a sheet need?
Roughly thirty for a 2400 by 1200 sheet: 300 millimetre centres on the perimeter and along each intermediate stud or joist. Ceilings take rather more, at 230 millimetre centres, because the board is fighting gravity rather than resting against a stud.
What thickness of board should I use?
Twelve and a half millimetres for walls and ceilings at standard stud and joist spacings, and 9.5 millimetres only where the framing is closer or the board is being laminated over an existing surface. Moisture-resistant board goes in bathrooms and fire-rated board where a compartment wall requires it.
Do I need to deduct openings?
For a single door in one wall it barely changes the sheet count and it is safer not to. Across a whole house the deductions are significant, and you will still have useful offcuts above and below windows, which is why the allowance stays at ten per cent.
Why two layers?
A second layer with joints staggered against the first adds mass and breaks the sound path, which is the usual way to improve acoustic separation between rooms. It is also a common way to meet a fire resistance requirement. Both layers are counted here.
Plasterboard sheet reference
| Net area | 2400 × 1200 | 2400 × 900 | 1800 × 900 | 1200 × 900 |
|---|---|---|---|---|
| 5 m² | 2 | 3 | 4 | 6 |
| 10 m² | 4 | 6 | 7 | 11 |
| 15 m² | 6 | 8 | 11 | 16 |
| 20 m² | 8 | 11 | 14 | 21 |
| 30 m² | 12 | 16 | 21 | 31 |
| 40 m² | 16 | 21 | 28 | 41 |
| 60 m² | 23 | 31 | 41 | 62 |
| 90 m² | 35 | 46 | 62 | 92 |
A 2400 × 1200 sheet is 2.88 m²; a 1200 × 900 sheet is 1.08 m².