Plasterboard Calculator

How This Is Calculated

The area to board is your length times height, minus an average deduction for each door (1.5m²) and window (1.2m²) you enter. That net area, with your wastage allowance added, is divided by the area of one board to get the number of sheets, rounded up.

Screws are worked out from the fixing grid your stud spacing and screw spacing create: a screw goes in roughly every screw-spacing distance along every stud line, and stud lines occur every stud-spacing distance across the area. Multiplying those two spacings gives the area covered per screw, and dividing the net area by that figure gives the total screw count.

Common Questions

Which board thickness should I use?

12.5mm is the standard choice for most stud walls and ceilings and gives better sound and fire resistance. 9.5mm is lighter and easier to handle overhead, which is why it's sometimes preferred for ceilings, but check what your local building control or the room's use requires before choosing the thinner option.

Why does stud spacing affect the number of screws?

Screws can only go into the timber studs or joists behind the board, not the board alone, so the number of fixing lines across a wall depends entirely on how far apart those studs are. Closer stud spacing means more fixing lines and more screws for the same area.

Do I need jointing compound and tape as well?

Yes - every joint between boards needs filling and taping (or using a combined jointing compound) to hide the seam and give a flat surface ready for skimming or painting. This calculator focuses on boards and screws; budget separately for jointing compound and joint tape based on the total length of joints in your layout.

Should I stagger the joints between boards?

Yes, on both walls and ceilings. Lining up joints from one row directly above the next creates a continuous weak line that's more likely to crack, so joints are staggered by at least 300-400mm between rows for a stronger, more stable finish.