How many insulation batts you need for ceiling, walls or floor. Matched to Australian NCC climate zones with recommended R-values and standard AU batt sizes.
This calculator uses standard Australian batt dimensions — 430 mm wide (suits 450 mm stud spacing) and 580 mm wide (suits 600 mm stud spacing) — with a length of 1,160 mm, which is the most common length for bulk insulation batts sold in Australia.
A 10% waste margin is added automatically to cover cut pieces around joists, pipes, obstacles and edges. For heavily obstructed ceilings or walls with lots of windows, consider increasing your order by a further 5%.
The National Construction Code (NCC) sets minimum insulation requirements based on eight climate zones. Your state or territory can span multiple zones, but the table below shows typical recommendations for the most common zone in each state.
| State / Territory | Typical zone | Ceiling (min) | Walls (min) | Floor (min) |
|---|---|---|---|---|
| NT (Darwin) | Zone 1 | R2.7 | R1.5 | R1.0 |
| QLD (Brisbane) | Zone 2 | R3.2 | R1.5 | R1.0 |
| NSW (Sydney) | Zone 3 | R3.5 | R1.5 | R1.5 |
| SA (Adelaide) | Zone 4 | R4.1 | R2.0 | R1.5 |
| WA (Perth) | Zone 4 | R4.1 | R2.0 | R1.5 |
| VIC (Melbourne) | Zone 5 | R4.1 | R2.5 | R2.0 |
| ACT (Canberra) | Zone 6 | R5.1 | R2.5 | R2.5 |
| TAS (Hobart) | Zone 6–7 | R5.1 | R2.5 | R2.5 |
430 mm batts suit wall cavities and ceiling joists spaced at 450 mm centres — the standard for most timber-framed homes built before the 1990s.
580 mm batts suit framing at 600 mm centres, which is common in steel-framed homes and many newer construction builds. Check the spacing between your joists or studs before ordering — measure between the inner edges of the framing.
The NCC requires different R-values for each building element. Ceilings lose the most heat in winter and gain the most in summer, so they require the highest R-value. Floors typically require less insulation in warmer climates but are important in cool and alpine zones. Walls sit in between.
In practice, it's always worth exceeding the minimum — going from R3.5 to R4.0 in a ceiling adds very little cost but meaningfully reduces ongoing energy bills.
Most Australian insulation manufacturers — including Bradford, Fletcher Insulation, and Knauf — package ceiling and wall batts in packs of 6 to 12. Pack size varies by R-value: higher R-value batts are thicker, so fewer fit in a pack. Check the product label at your hardware store or builder's merchant, and use the pack size field above to match your specific product.