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
Recommended cooling capacity
Still to answer: room dimensions, insulation quality, sun exposure, climate zone and room type. Your result appears here.
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.
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
What a ceiling fan does, and doesn't
A fan doesn't cool a room - it moves air across your skin, which makes the same temperature feel cooler, and it costs very little to run. That's worth having alongside an air conditioner. It doesn't change the capacity the room needs: size the unit for the room, then let the fan make it comfortable sooner.
An open-plan room is bigger than it measures
If your living area flows into a kitchen, dining space, or hallway, the air moves between all of them - so add the combined volume, not only the room the aircon will sit in. For open-plan areas over 60m², ducted systems often outperform a single split system.
Cool the rooms you're in, not the ones you aren't
Multi-zone systems, or several smaller split systems, often beat one large unit in a home where the 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.