How the calculation works
The formulas
Thickness converts net area to material volume. Pack coverage is entered independently from the product label; waste applies to area before whole-pack rounding.
Net volume = area × thickness
Required area = area × (1 + waste/100)
Packs = ceil(required area ÷ pack coverage)
Assumptions to check
- Thickness alone does not determine U-value, R-value, fire performance, or condensation risk.
- Pack coverage must match the product thickness being purchased.
A worked example
40 m² at 100 mm has 4 m³ net volume. With 5% waste and 5.4 m² packs, buy 8 packs (43.2 m²).