Air conditioner size calculator
2.5–9.4
kilowatts, sized honestly
Recommended size
3.5 kW
Calculated load ≈ 3.0 kW for 25 m²
Typical installed price
$2,000 – $2,900
Standard back-to-back split, 2026
Free. No calls until you ask.
The quick table, if you hate sliders
Typical insulated room, standard ceiling, average sun. Adjust up one size for hard west glass, raked ceilings or no insulation.
| Room size | Typical rooms | Split size | Installed, 2026 |
|---|---|---|---|
| 10–20 m² | Bedroom, study | 2.5 kW | $1,800 – $2,600 |
| 20–30 m² | Big bedroom, lounge | 3.5 kW | $2,000 – $2,900 |
| 30–45 m² | Living room, living + dining | 5.0 kW | $2,400 – $3,600 |
| 45–60 m² | Open plan | 7.1 kW | $2,900 – $4,800 |
| 60+ m² | Large open plan, several rooms | Multi-head or ducted | $4,500 – $17,500 |
The method behind both the table and the calculator: 100–140 watts of cooling per square metre, adjusted for ceilings, glass, insulation and climate. The full reasoning is in the sizing guide. Your installer confirms the final size on a site visit — if they never asked about windows, they guessed.
FAQ
Sizing questions, answered straight
What size air conditioner do I need for a 4x4 room?
A 4x4 metre room is 16 m². With standard ceilings and average sun, that is a calculated load of roughly 1.9–2.3 kW, so a 2.5 kW split covers it comfortably. Only step up to 3.5 kW if the room cops hard western sun or has no insulation.
What size air conditioner do I need for a 20m² bedroom?
Around 2.4–2.8 kW of calculated load, which lands on a 2.5 kW split in good conditions or a 3.5 kW with high ceilings or big glass. The 3.5 kW is also fine here — it is one of the cheapest sizes per kilowatt sold in Australia.
Is it better to oversize or undersize an air conditioner?
Neither, but oversizing is the more common and more expensive mistake. An oversized inverter short-cycles: it blasts the room cold, shuts down before it dehumidifies, and leaves the air clammy. Slightly under is usually more comfortable than well over. Size from the room, not from fear.
How many square metres does a 2.5kW air conditioner cool?
Roughly 10–20 m² in a typical insulated Australian room — a bedroom, study or small lounge. Push past 20 m², add a raked ceiling or hot western glass, and you are into 3.5 kW territory.
Do I need a bigger air conditioner in Queensland?
A little. Hot, humid climates add roughly 10% to the load, and humidity makes correct sizing matter more, not less — an oversized unit in Brisbane leaves the room cold and damp. Use the climate setting in the calculator and let it do the adjusting.
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