Plasterboard — commonly called gyprock — is estimated from the total wall and ceiling area, then converted to sheets. This guide shows the calculation, explains why fewer joints save real labour, and covers choosing the right board type for wet areas and fire ratings.
Plasterboard — often called gyprock after the common brand — is estimated from the total area of walls and ceilings you are lining, in square metres. For a room, calculate the wall area (perimeter times height) and the ceiling area (length times width) and add them together.
A 4m by 5m room with 2.4 metre ceilings has about 43 square metres of wall plus 20 square metres of ceiling, for roughly 63 square metres total. Our square metre calculator handles the measuring.
Plasterboard comes in standard sheets, commonly 1200mm wide by lengths from 2400mm up. A 1.2m by 2.4m sheet covers 2.88 square metres. Divide your total area by the sheet coverage and round up.
Sheets = Total area ÷ Sheet coverage, then add wastage
Our 63 square metre room needs 63 ÷ 2.88 ≈ 22 sheets before wastage. Because walls and ceilings rarely divide neatly into sheet sizes, add around 10 to 15% for cuts and offcuts — so order about 25 sheets. Larger sheets mean fewer joints to finish, which is why installers often prefer the longest sheets that will fit through the door.
Not all plasterboard is the same, and using the wrong type is a costly mistake. Standard board suits most walls and ceilings. Wet-area board (water-resistant) is required for bathrooms, laundries and kitchens. Fire-rated board is needed where the building code requires it, such as some walls between rooms or dwellings. Acoustic board reduces sound transfer. Specify the right board for each area rather than lining the whole house in standard sheets.
Sheets alone do not finish a room. You also need joint compound (base coat and topping), paper or fibreglass jointing tape, corner beads for external corners, and plenty of plasterboard screws or nails. Compound is estimated by the number and length of joints, and it is easy to under-buy — running out of topping compound mid-job stalls the whole room. Buy generously; leftover compound stores reasonably well.
Ceiling sheeting uses the same maths but is far more demanding to install — sheets are heavy, held overhead, and must be fixed to ceiling joists or battens at the correct spacing. This is where many DIYers decide to bring in a professional, and where a plasterboard lifter (a hire tool) earns its keep. Factor the extra difficulty of ceilings into your plan even though the estimate is straightforward.
Calculate walls and ceilings separately, choose the correct board type for each area, convert to sheets, add 10 to 15% wastage, and buy compound and fixings generously. Because plasterboard is awkward to transport in small quantities, getting the estimate right the first time — rather than making repeat trips — saves both money and a great deal of hassle.
How many plasterboard sheets do I need?
Add the wall area (perimeter times height) and ceiling area (length times width) in square metres, then divide by the sheet coverage — a 1.2m by 2.4m sheet covers 2.88 square metres. Round up and add 10 to 15 per cent for cuts. A typical room of 63 square metres needs about 25 sheets.
What type of plasterboard do I need?
Standard board suits most walls and ceilings, wet-area (water-resistant) board is required for bathrooms, laundries and kitchens, fire-rated board where the building code requires it, and acoustic board to reduce sound. Specify the right board for each area.
Why do larger sheets save money?
Every joint between sheets must be taped, set with compound, sanded and coated. Larger sheets mean fewer joints and much less finishing labour, which is usually the bigger cost — so installers prefer the longest sheets that will fit through the door.
What else do I need besides sheets?
Joint compound (base and topping), jointing tape, corner beads, and plenty of screws or nails. Compound is easy to under-buy — running out mid-job stalls the room — so buy generously, as leftover compound stores reasonably well.
Is ceiling plasterboard harder to install?
Yes. Ceiling sheets are heavy, held overhead, and must be fixed to joists or battens at the correct spacing. This is where many DIYers bring in a professional, and where a hired plasterboard lifter earns its keep.