Air conditioner size calculator
Work out the kW capacity your room needs. Under-sized aircons struggle to cool, over-sized ones waste money and leave rooms damp.
Room dimensions
Measure the room, not just the floor area. Ceiling height defaults to 2.4m — change it if yours differs.
Room characteristics
Insulation quality
Sun exposure
Climate zone
Room type
Why sizing matters
What happens if you get the size wrong?
−Too small
- Struggles to reach set temperature
- Runs constantly, uses more power
- Compressor wears out faster
- Humidity stays high
+Too big
- Rapid cycling on and off
- Doesn't dehumidify properly — leaves the room cold and clammy
- Costs more upfront for capacity you won't use
- Bigger electricity spikes each cycle
Things the calculator doesn't cover
Ceiling fans change everything
A ceiling fan can make a room feel 3–4°C cooler with minimal electricity use. If your room already has a fan, you can often go one size smaller on the aircon and still be comfortable.
Open plan is trickier than this
If your living area flows into a kitchen, dining space, or hallway, factor in the combined volume — not just the room where the aircon will sit. For open plan areas over 60m², ducted systems often outperform a single split system.
Zone it if you can
Multi-zone systems or multiple smaller split systems often beat one large unit, particularly in homes where rooms aren't all occupied at once. Cooling empty rooms is money burned.
Installation affects performance as much as capacity
A correctly-sized aircon with poor installation will underperform. Ask installers about refrigerant line length limits, outdoor unit placement (shading matters), and whether they'll vacuum the system properly before charging.
Ready to find an air conditioner that fits?
Our quiz matches your requirements to specific models from Australian retailers — including energy ratings and price comparisons.
Start the aircon quiz →This calculator provides an estimate only. Final system sizing should be confirmed by a licensed installer who can assess your specific home, including factors like roof colour, floor type, ceiling insulation depth, and neighbouring buildings. Multipliers are based on Australian industry guidelines and are intended as a starting point, not a substitute for a professional load calculation.