Enter area, product type and install complexity to get the exact number of batts or rolls to order including waste allowance.
Standard glasswool R2.6 batts (1160 × 580 mm) each cover 0.67 m². For 100 m² with 10% waste: 100 / 0.67 × 1.10 = 164 batts. This calculator works it out for any batt size and waste level.
Use 5% waste for simple rectangular ceilings with few obstructions. Use 10% for rooms with some pipes, cables or irregular shapes. Use 15% for complex installs with many rafters, joists, recessed lights and penetrations that require cutting.
Batts are pre-cut panels that are placed between joists by hand — faster to install and no specialist equipment needed. Loose-fill is blown in with a machine — better for already-finished ceilings or complex spaces, achieves higher R-values easily, but needs specialist equipment and protective measures.