How many sheets of plasterboard for a 4 m by 3 m room?

With the planner's example boards, 1.2 m × 2.4 m, one layer and 10% extra, a room 2.4 m high with one door and one window takes 12 boards for the walls, 5 for the ceiling and 17 for both. All of those figures are generic examples, not a product or a system specification: the label and the specification replace them.

How many sheets of plasterboard for a ceiling?

A 4 m × 3 m ceiling is 12 m², or 13.2 m² with 10% extra. Divided by 2.88 m² for each 1.2 m × 2.4 m example board that is 4.58, so 5 boards. Nothing is taken off the ceiling.

How much extra plasterboard should I allow for cuts?

BuildBatch starts at 10%, as a labelled example and not a published rule. For the walls and ceiling of the 4 m × 3 m room together, 0% gives 15 boards, 10% gives 17 and 15% gives 18, so change it to suit the layout you have planned.

Does BuildBatch count the screws?

No. Screw type, length and spacing depend on the boards, the layers, the framing and the system, so the line stays Check first. BuildBatch counts the boards that need fixing instead: 17 in the example room.

How many sheets of plasterboard do I need?

The planner counts whole boards, or sheets: the area of the walls and ceiling you choose, times the layers, plus an allowance for cuts, divided by the area of one board and rounded up. At its example figures, 1.2 m × 2.4 m boards, one layer and 10% extra, a room 4 m × 3 m and 2.4 m high takes 12 boards for its walls, 5 for its ceiling and 17 for both.

The sum

Boards = surface area × layers × (1 + extra ÷ 100) ÷ one board’s area, rounded up to a whole board.

Surface area. For walls, the distance round the room times its height, less the doors and windows you enter. For a ceiling, length times width, with nothing taken off. With both chosen, the two are added.
Layers. A whole number, from 1 to 4, that comes from the system specification.
Extra. The allowance for cuts, from 0% to 50%. BuildBatch starts at 10%.
One board’s area. Width times length, from the board’s label.

The count is rounded once, at the end, across the surfaces you chose. It is an area count, not a cutting layout: check the layout before buying, especially round openings and on ceilings.

Board sizes

The planner holds one example board, 1.2 m × 2.4 m, which is 2.88 m². It is a generic example, not the size of any product. It takes any width from 0.3 m to 2 m and any length from 0.6 m to 6 m, so the size on your boards’ label replaces it.

The same room with two other sizes typed in. They are figures entered for this table, not a list of what is sold:

Board	One board covers	Walls	Ceiling	Walls and ceiling
1.2 m × 2.4 m (the example)	2.88 m²	12	5	17
0.9 m × 1.8 m	1.62 m²	21	9	30
1.2 m × 2.7 m	3.24 m²	11	5	15

With the 1.2 m × 2.7 m board, the walls and the ceiling counted separately come to 11 + 5 = 16, and counted together to 15. The planner rounds up once, across both surfaces, and an area count does not know whether a piece cut for a wall can be used on the ceiling.

Worked example

A room 4 m × 3 m and 2.4 m high, with one internal door 762 mm × 1981 mm and one window 1.2 m × 1.1 m. The example board, one layer and 10% extra.

Working	Walls	Ceiling	Walls and ceiling
Surface area	30.77 m²	12 m²	42.77 m²
With 10% extra	33.848 m²	13.2 m²	47.048 m²
Divided by 2.88 m²	11.75	4.58	16.34
Boards to buy	12	5	17
Left over	0.712 m²	1.2 m²	1.912 m²

The walls are 14 m round × 2.4 m high, 33.6 m², less 2.83 m² for the door and window. The ceiling is 4 m × 3 m.

What changes the answer

The layers. Two layers on the walls and ceiling make 94.095 m² with the extra, which is 32.67 boards, so 33.
The extra. The same room, walls and ceiling together: 15 boards at 0%, 17 at 10% and 18 at 15%.
The layout. Narrow returns, staggered joints and awkward openings can need more boards than the area shows.

What else the planner lists

The lines BuildBatch lists for boarding, with the mark each starts with. “Check first” means it may need buying, and something the list cannot know decides it.

Item	Starts as	Why it is on the list
Plasterboard, in whole boards	Need	The count above
Finish plaster, in whole bags	Need, once skim is chosen and a bag’s coverage is entered	At the planner’s 10 m² a bag, a generic example, the 42.77 m² here takes 5 bags. Without a coverage it is Check first
Jointing compound, or a “Board finish” line	Check first	Tape and joint, or a finish not yet decided: the layout, the joints and the system decide the amount
Joint tape	Check first	Board joints are reinforced before the finish goes on
Angle beads and stop beads	Check first	External corners and exposed finish edges need the bead specified for the finish
Plasterboard adhesive	Need, if adhesive is chosen for walls and a bag’s boards are entered	Walls only. At 2 boards a bag, a generic example, the 12 wall boards take 6 bags
Screws and suitable support	Check first. Not needed for walls only, when adhesive is chosen	BuildBatch does not choose framing, centres, screw spacing or structural support
Tape measure, straight edge, board knife, rasp and screw gun	Need	To measure, score, trim and fix the boards
Board lift or enough safe lifting help	Check first, for a ceiling	Full plasterboards are heavy and awkward overhead. Plan how each board will be raised and held before starting
Eye protection, gloves and suitable dust protection	Need	Cutting and sanding board and dry finish makes dust; boards are heavy and edges can be sharp

What the planner does not decide

It does not choose a board type, framing, fire or sound performance, moisture resistance, fixing centres or structural support. Those come from one complete system specification, and room measurements cannot decide them.

Do it with BuildBatch

Open the plasterboard calculator, type the room, add the doors and windows, and choose walls, ceiling or both. Enter the board’s size, the layers and the extra from your own board and specification. You get the boards and every other line above, each marked Need or Check first, with the reason it is there.

What this guide does not cover

Which board, thickness or layers a wall or ceiling needs. How to fix the boards. Plastering, skimming and jointing. A cutting layout for awkward walls. Taking down old plaster or boards.