How the calculation works
Wall area is the room perimeter multiplied by wall height, less the area of major openings. The net area is increased by the selected waste allowance, then divided by the area of one sheet and rounded up.
Worked example
For a 5 m × 4 m room with 2.4 m walls and 6 m² of openings, net wall area is 37.2 m². A 2.4 m × 1.2 m sheet covers 2.88 m². With 10% allowance, the planning area is 40.92 m², which rounds to 15 sheets.
Planning note: Sheet count depends on layout, ceiling height, offcuts, sheet orientation and the actual board product. This calculator is not a framing or fire-rating design.
Common mistakes
- Forgetting large doors or windows.
- Using the package dimensions incorrectly.
- Assuming every offcut can be reused.
FAQ
Does this include the ceiling?
No. Add the ceiling as a separate rectangular area if required.
How much waste should I use?
Use a project-appropriate allowance. Rooms with many corners or small pieces may need more than a simple rectangular room.