About this calculator
Sheets for a whole room, walls and ceiling, with doors and windows deducted, plus the screws, scrim and multi-finish or jointing compound to finish them.
How it’s calculated
Wall area = perimeter × height − (doors × 1.9 m²) − (windows × 1.5 m²). Add the ceiling, add waste, and divide by the sheet area.
Finishing rates: a 25 kg bag of multi-finish skims about 10 m² at 2 mm. Scrim runs about 1.25 m per m² of board.
Worked example
With these inputs:
- Room length
- 4.2 m
- Room width
- 3.6 m
- Wall height
- 2.4 m
- Doors
- 1
- Windows
- 2
- Include ceiling
- Yes
- Sheet size
- 2400 × 1200 mm
- Finish
- Full skim coat
- Waste allowance
- 12%
the result is:
- Plasterboard sheets
- 19 sheets
- Wall area (net)
- 32.54 m²
- Ceiling area
- 15.12 m²
Tips from the trade
- Hang boards with the paper (ivory) side out, and stagger the end joints.
- Longer sheets mean fewer joints but need more hands.
- Don’t deduct small openings. The offcuts rarely get used.
Common questions
How many plasterboards for a 3.6 × 3.6 m room?
With 2.4 m walls and a ceiling: about 15–16 boards of 2400 × 1200 including waste.
Results are estimates for planning and pricing. Check quantities against your drawings, the manufacturer’s data and the Building Regulations before ordering.