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Insulation Batts Calculator

Packs of ceiling, wall or underfloor batts by R-value. Metric units, change any unit beside its field.

Measurements

From the pack label. Leave at 0 to use a typical figure for the R-value.
%
Extra for cuts, breakage and spillage.

About this calculator

Packs of glasswool or polyester batts for a ceiling, wall or underfloor at the R-value you pick.

How it’s calculated

Packs = area × (1 + waste) ÷ coverage per pack. Pack coverage varies a lot by brand and batt width, so enter the figure from the label for an exact count.

Worked example

With these inputs:

Area length
8 m
Area width
6 m
Batt R-value
R4.0 ceiling batts
Coverage per pack (m²)
0
Waste allowance
5%

the result is:

Packs of R4.0 batts
8 packs
Coverage per pack
6.5 m² (typical; check the label)

Tips from the trade

  • The R-value you need depends on your NCC climate zone and the home’s energy rating. Ceilings commonly take R3.5–R6.0 batts and 90 mm stud walls R2.0–R2.7.
  • Keep insulation clear of eaves vents and recessed light fittings unless they are rated for contact.
  • Board out over the top layer only if you raise the boards on legs. Compressed insulation loses performance.

Results are estimates for planning and pricing. Check quantities against your drawings, the manufacturer’s data and the NCC and Australian Standards before ordering.