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What size aircon
do you need?

Two taps: what you're cooling and your city. We give you the size, and what it costs installed where you live.

What are you cooling?

Your city

Your size

Answer both questions and your recommendation appears here instantly.

Transparent maths

How we calculate this

The industry rule

120–150 watts of cooling per square metre, the same sizing rule installers and Australia's official consumer guidance use as the starting point.

Adjusted for your climate

Hot-climate cities get extra capacity headroom so the unit still holds temperature on a 43°C afternoon, when budget sizing falls over.

Rounded to real units

Results map to the capacities actually sold, 2.5 to 9.5kW, and when you sit between sizes we round up. An undersized unit working flat-out costs more and dies younger.

A guide, not a site survey: ceiling height, insulation and glazing all move the answer, which is why installers confirm sizing on site before you commit to anything.

How the sizing works

We size at 120–150 watts of cooling per square metre (sqm), the band Australian installers actually use, then adjust for sun load and your city's summer peaks. Hot inland climates (Penrith-style summers, Darwin humidity) need genuine capacity headroom: a unit that never gets to loaf on a 42°C afternoon is a unit that fails early.

Room	Typical size	Standard unit
Bedroom to 15m²	2.0–2.5kW	2.5kW
Bedroom / study to 25m²	2.5–3.5kW	3.5kW
Lounge to 35m²	4.0–5.0kW	5.0kW
Large open plan 50m²+	6.0–8.0kW	7.0–8.0kW
Whole home	Ducted	12–16kW zoned system

Sizing questions

How many kW of cooling do I need per square metre?

The working rule is 120–150 watts per square metre for typical Australian rooms, so a 30m² living room needs roughly 4–4.5kW. West-facing glass, poor insulation or hot inland climates push you to the top of that band or a size beyond it.

Is it bad to oversize an air conditioner?

Mildly, an oversized unit cycles on and off more, dehumidifies worse and costs more upfront. But undersizing is the expensive mistake: a unit running flat-out on a 40°C day never reaches temperature and wears out sooner. When between sizes, most installers round up.

Do these sizes account for ceiling height?

The calculator assumes standard 2.4m ceilings. Add roughly 10% capacity for 2.7m ceilings and 20% for 3m+, worth flagging to installers for older homes with high ceilings.

Get quotes for exactly this unit

Your size recommendation is attached to the lead, installers quote the right system first time.

What size aircon do you need?