Free tool
Plasterboard calculator
Room dimensions in, sheets, screws and compound out.
Sheeting a room is mostly arithmetic you can do at the merchant's counter, as long as you remember to take the windows out and put the cuts back in. This does both.
The sum
Wall area is the total length of the walls times the height. Take off the doors and windows, add the ceiling if you are sheeting it, then add ten per cent for cuts and divide by the sheet size.
A room with 24 metres of wall at 2.4 metres high is 57.6 square metres. Deduct 4 square metres for a door and a window and you have 53.6. Add ten per cent and divide by a 1.2 by 3.6 sheet, which is 4.32 square metres, and it comes to about fourteen sheets.
Sheet horizontally
On a standard 2.4 metre wall, two sheets laid horizontally cover floor to ceiling with one join running around the room at waist height. Sheeting vertically instead gives you a join every 1.2 metres, floor to ceiling.
The horizontal join is easier to hide, and that matters more than it sounds. A vertical join catches side light from a window and shows every imperfection down its whole length. A horizontal one at waist height sits where light rakes across it least, and it is a far more comfortable height to set.
Ten per cent, and why
The allowance is not for mistakes, it is for geometry. A sheet cut around a window leaves an offcut with a notch in it that will not fit anywhere else. Rooms with lots of openings, a stairwell, or angled ceilings run higher than ten per cent.
The other materials
Screws come out at roughly thirty to a sheet with fixings at 300mm centres on studs at 450. One 20 kilogram bag of base coat sets somewhere near 25 square metres of joint. Paper tape runs about 30 metres per 25 square metres of wall. These are ordering estimates, not specifications, and the fixing guide for the board you actually buy is the authority.
Which board where
Use the water resistant board in wet areas, and check whether the room needs fire rated or acoustic board before you order the standard sheets. In both New South Wales and Victoria, wet area construction is covered by the building code rather than by preference, and getting it wrong in a bathroom is a demolition job rather than a repaint.
Common questions
How many sheets of plasterboard do I need for a room?
Total wall length times ceiling height, less the doors and windows, plus the ceiling if you are sheeting it, plus about ten per cent for cuts, divided by the sheet area. A standard 1.2 by 3.6 metre sheet is 4.32 square metres. The calculator above does it from your dimensions.
Should plasterboard be hung horizontally or vertically?
Horizontally in most domestic rooms. Two sheets cover a 2.4 metre wall with a single join at waist height, which is far easier to set invisibly than a floor to ceiling join. Vertical joins catch side light from windows and show along their whole length.
How many screws per sheet of plasterboard?
Roughly thirty a sheet with fixings at 300mm centres on studs at 450mm centres. Treat it as an ordering estimate and follow the fixing guide for the board you buy, which sets the actual spacing for walls, ceilings and fire or acoustic rated systems.
Can I use normal plasterboard in a bathroom?
No. Wet areas need the water resistant board and a compliant waterproofing system, and in both NSW and Victoria that is set by the building code rather than by preference. Getting it wrong in a bathroom means pulling the room apart later rather than repainting it.