How the calculation works
The formulas
Add rectangular surfaces and subtract openings. The result divides adjusted area by sheet area and rounds up. It is a quantity estimate, not an optimized cutting or joint-staggering plan.
Net area = total surface area − opening area
Sheets = ceil(net area × (1 + waste/100) ÷ sheet area)
Purchase area = sheets × sheet area
Assumptions to check
- One layer is counted. Add each layer separately if the assembly requires more.
- Studs, fixings, joint compound, fire rating, and acoustic performance are not calculated.
A worked example
A 12 m² net surface plus 10% waste requires 13.2 m². A 2.4 × 1.2 m sheet has 2.88 m²; buy 5 sheets (14.4 m²).