What size air conditioner do I need? This air conditioner size calculator works out the cooling capacity in kW from your room size and ceiling height, picks the split system size to look at, and shows what it costs installed in your city.
Enter the room, or tap a common room to start.
Your measurements
Estimated cost, Australia
$1,800 to $3,500 typical $2,500
Your numbers
- Room area
- 30 m²
- Cooling capacity needed at 150 W per m²
- 4.5 kW
- Split system size to look at
- 5 kW, the smallest in our guide that covers it
| Price row | Quantity | Rate | Low to high |
|---|---|---|---|
| Split system 5 kW (supply + install) | 1 | $1,800 to $3,500 installed | $1,800 to $3,500 |
Rates are the low, typical and high figures in our air conditioning price guide, prices verified October 2026. An estimate only: get quotes to price your job.
Type the total on your quote to see how it compares with this estimate.
This job in 15 cities: typical $2,250 in Hobart to $2,875 in Sydney
| City | Low to high | Typical |
|---|---|---|
| Hobart | $1,625 to $3,150 | $2,250 |
| Adelaide | $1,650 to $3,225 | $2,300 |
| Geelong | $1,675 to $3,250 | $2,325 |
| Newcastle | $1,700 to $3,325 | $2,375 |
| Sunshine Coast | $1,750 to $3,400 | $2,425 |
| Gold Coast | $1,775 to $3,425 | $2,450 |
| Brisbane | $1,800 to $3,500 | $2,500 |
| Darwin | $1,800 to $3,500 | $2,500 |
| Byron Bay | $1,900 to $3,675 | $2,625 |
| Melbourne | $1,900 to $3,675 | $2,625 |
| Perth | $1,900 to $3,675 | $2,625 |
| Townsville | $1,950 to $3,775 | $2,700 |
| Wollongong | $1,950 to $3,775 | $2,700 |
| Canberra | $1,975 to $3,850 | $2,750 |
| Sydney | $2,075 to $4,025 | $2,875 |
Each city is priced from the rows in its own guide, cheapest typical figure first.
What size air conditioner do I need?
- Work out the floor area: length × width.
- Allow for the ceiling. ActronAir's guide uses 150 W per m² for a 2.4 m ceiling, 160 W for 2.7 m and 175 W for 3 m.
- Pick the next size up from the split systems on sale.
| Room | Cooling needed | Installed cost |
|---|---|---|
| Bedroom, 4 m × 3.5 m | 2.1 kW | $1,200 to $2,500 |
| Living room, 6 m × 5 m | 4.5 kW | $1,800 to $3,500 |
| Open-plan living, 9 m × 6 m | 8.1 kW | $3,000 to $5,500 |
CHOICE notes that the right size also depends on your climate and insulation, so treat this as the starting point to discuss with an installer.
How the calculation works
Size. ActronAir's rule is to multiply the daytime living area in square metres by 150 watts for a 2.4 m ceiling, 160 watts for 2.7 m and 175 watts for 3 m. The example the calculator opens with is 6 m × 5 m with a 2.4 m ceiling: 30 m², which needs 4.5 kW. Energy Victoria notes that ceilings higher than the standard 2.4 m need more energy to heat and cool.
Treat it as an upper figure. CHOICE says most commercial calculators or guides recommend 3.5 to 5 kilowatts for a 30 square metre room, which is often more capacity than needed: its own estimate for that room ranges from 1.8 kilowatts in Hobart to 3 in Perth, and roof insulation brings it from 2.9 to 2.3 kilowatts. Ask the installer to size the unit for your room, its insulation and the sun it gets.
Cost is the supply-and-install row for that split system size in your city, or the install-only row if you already have the unit. Removing an old unit adds its own row.
Source for the figures that are not prices: ActronAir (cooling watts per square metre by ceiling height); CHOICE (the capacity CHOICE estimates for a 30 square metre room); Energy Victoria (the standard ceiling height), checked October 2026.
Split system size by room size
At ActronAir's 150 watts per square metre for a standard 2.4 m ceiling.
| Room | Cooling needed | Split system to look at |
|---|---|---|
| 9 m² | 1.4 kW | 2.5 kW, the smallest in our guide that covers it |
| 14 m² | 2.1 kW | 2.5 kW, the smallest in our guide that covers it |
| 20 m² | 3 kW | 3.5 kW, the smallest in our guide that covers it |
| 30 m² | 4.5 kW | 5 kW, the smallest in our guide that covers it |
| 42 m² | 6.3 kW | 7 kW, the smallest in our guide that covers it |
| 56 m² | 8.4 kW | 9 kW, the smallest in our guide that covers it |
Air Conditioning rates the calculator uses
These are the national figures from our air conditioning price guide. Pick a city in the calculator and it switches to the same rows from that city's guide.
| Price row | Low | Typical | High |
|---|---|---|---|
| Split system 2.5 kW (supply + install) | $1,200 | $1,800 | $2,500 installed |
| Split system 3.5 kW (supply + install) | $1,400 | $2,100 | $2,800 installed |
| Split system 5 kW (supply + install) | $1,800 | $2,500 | $3,500 installed |
| Split system 7 kW (supply + install) | $2,200 | $3,200 | $4,500 installed |
| Split system 9 kW (supply + install) | $3,000 | $4,200 | $5,500 installed |
| Split system install only (customer-supplied unit) | $700 | $950 | $1,500 installed |
| Removal & disposal | $100 | $200 | $350 per unit |
| Ducted system (basic) | $8,000 | $11,000 | $14,000 installed |
Air Conditioning prices by city
SydneyMelbourneBrisbanePerthAdelaideGold CoastCanberraHobartDarwinNewcastleGeelongSunshine CoastTownsvilleWollongongByron Bay
Frequently asked questions
What size air conditioner do I need?
Multiply the floor area by about 150 watts per square metre for a 2.4 m ceiling (ActronAir's rule), more for higher ceilings. A 6 m × 5 m room is 30 m² and needs 4.5 kW, so a 5 kW split system is the size to look at.
What size air conditioner for a 30 square metre room?
ActronAir's rule gives 4.5 kW. CHOICE puts it lower and by city: 2.3 kilowatts in Sydney, 2.8 in Melbourne, 2.6 in Brisbane, 3 in Perth, 2.8 in Adelaide and 2.9 in Darwin. It warns that guides recommending 3.5 to 5 kilowatts often oversize.
Does ceiling height change the size?
Yes. ActronAir uses 150 watts per square metre for a 2.4 m ceiling, 160 for 2.7 m and 175 for 3 m, and Energy Victoria notes ceilings higher than the 2.4 m standard need more energy to heat and cool.
Does insulation change the size?
CHOICE's example 30 square metre room needs 2.3 kilowatts with roof insulation and 2.9 kilowatts without it.
How much does a split system cost installed?
Our national guide lists a 2.5 kW split system at $1,200 to $2,500 supplied and installed, 5 kW at $1,800 to $3,500 and 7 kW at $2,200 to $4,500. Installing a unit you already have is $700 to $1,500.
What if my room needs more than one split system?
Above 9 kW the calculator suggests two split systems or ducted. Our national guide lists a basic ducted system at $8,000 to $14,000 installed.
What size air conditioner do I need for a bedroom?
A 4 m × 3.5 m bedroom with a 2.4 m ceiling needs about 2.1 kW of cooling at 150 W per m². The split system size to look at is 2.5 kW, the smallest in our guide that covers it.
An estimate is a starting point. Get quotes from local air conditioning businesses to price your job.
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