Plasterboard calculator
How many whole plasterboards to buy for the walls, ceiling or both, with finish materials and the checks that depend on the chosen system.
How the number is worked out
- Measure the surfaces. Wall area is the distance round the room times its height, less the doors and windows entered. Ceiling area is length times width.
- Choose the layers. One, two or more layers must come from the complete wall or ceiling system you are following.
- Add the extra for cuts. The planner starts at 10%, as a labelled example. Change it for the layout you have planned.
- Count whole boards. The area with the extra is divided by one board's area and rounded up.
- Count a finish only when its figure is known. For a skim, enter the coverage printed on the bag. Tape-and-joint materials stay as a check because the board layout decides the joint length.
This is an area estimate, not a cutting layout. Narrow returns, staggered joints and awkward openings can need more boards than an area calculation shows.
A worked example
A room 3 m by 2 m and 2.4 m high, with one door 0.8 m by 2 m. The example boards are 1.2 m by 2.4 m, one layer, with 10% extra. These are generic example figures, not a product or a system specification.
| Working | Walls | Walls and ceiling |
|---|---|---|
| Surface area | 22.4 m² | 28.4 m² |
| With 10% extra | 24.64 m² | 31.24 m² |
| One board covers | 2.88 m² | 2.88 m² |
| Boards to buy | 9 | 11 |
If a finish plaster bag covers 10 m² at the stated thickness, the 28.4 m² face needs 3 bags. That coverage is an example: use the figure on the chosen bag.
Mistakes that cost a board
- The complete system. Board type and thickness, layers, framing, fixing centres and joint treatment work together.
- What the construction must do. Fire, sound, moisture and impact performance cannot be chosen from room size alone.
- Whether the support is suitable. A ceiling needs a specified frame and fixing method. Adhesive is offered for suitable walls only, where the chosen system permits it.
- The board layout. Plan the joints, openings and small returns before buying. The visible allowance is there for you to change.
- How the boards will be moved and lifted. Full boards are heavy and awkward, especially overhead.
Questions
Does it choose the right plasterboard?
No. Room measurements cannot decide fire, sound, moisture or structural performance. Use a complete system specification for the construction and choose the board it names.
Does it make a cutting plan?
No. It counts boards by area, with a visible extra for cuts. Plan the board positions and joints before buying, especially for awkward walls and openings.
Are doors and windows taken off?
Yes. Openings entered for the room come off the wall area. Nothing comes off the ceiling.
Does it count screws?
No. Screw type, length and spacing depend on the specified board, layers, framing and performance. The list keeps them as a check instead of inventing a count.
Can adhesive be used on a ceiling?
No. The adhesive choice is for suitable masonry walls where the system permits it. A ceiling still shows support and fixings as a check.