Plasterboard calculator

How the sheet count is worked out

One sheet covers its length times its width in metres. A 2400 by 1200 mm sheet is 2.4 by 1.2, which is 2.88 square metres.

The area to cover, plus the waste allowance, is divided by the sheet area and rounded up. Thirty square metres with 10 per cent waste is 33 square metres, which is 12 sheets.

Waste is higher than most materials because a sheet cannot be joined anywhere. A cut along a wall leaves an offcut that often will not fit anywhere else.

Worked example

Thirty square metres with a 2.4 by 1.2 metre sheet and 10 per cent waste needs 12 sheets.

The same area in 1800 by 900 mm sheets, which cover 1.62 square metres, needs 21 sheets. Smaller sheets are easier to handle alone but waste more.

Board size, thickness and handling

A 2400 by 1200 by 12.5 mm sheet weighs about 22 kg, which is manageable for two people but awkward alone. Thicker or moisture resistant boards are heavier.

Ceilings usually take 12.5 mm and walls 12.5 mm, with 15 mm or a double layer where fire or sound performance is needed.

Order in the length that spans the most joints. Longer sheets mean fewer joints to tape, which is the slowest part of the job.

Limits of this calculator

It counts sheets only. It does not include screws, joint tape, jointing compound, corner beads or adhesive.

It does not account for a room where every sheet has to be cut, which wastes far more than 10 per cent.

It does not check the board type, the fixing centres or the fire and acoustic requirements.

For the paint that goes on afterwards, use the paint calculator.

Inputs for the plasterboard calculator