What Size Air Conditioner do i Need? (Free Calculator)

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Summers are hot in Australia, especially in Perth. There is no arguing against that. It’s truly a hassle season especially when you opt to stay indoors in your home instead of going to beaches to cool down. Good thing there are air conditioners to cool your house. But what type and size do you need?

Types of Air Conditioners

There are two common types of air conditioning in Australia. Ducted air conditioning and Split system air conditioners. Ducted air conditioning systems are more complex to size correctly and this article will not cover that. We will help you out and let you know for free if you send us a floor plan though.

If you choose to buy a split system, its quite easy to work out the size for the room because a split usually just powers one room each. In short, A split system air conditioner is composed of two major units–the indoor wall-mounted unit that blows cools the air inside your home and the outdoor unit that releases the heat from the inside.

What Size Air Conditioner Do I Need?

The size of your air conditioner depends on the size of the room to be cooled. Generally, you will need about 1.25-1.7 kilowatts of power per 10 sqm if the ceiling height is standard. To work out what size you need multiply the width by length of the room to get you floor space.

We have put together this indicative table to show what size air conditioner you may need.

Room Size (m²Cooling Capacity
102.1 kW
152.5 kW
203.25 kW
253.5 kW
304.0 kW
405.0 kW
506.0 kW
607.5 kW
709.0 kW

Please be aware that this table is indicative based on an average home and may not apply to your home’s circumstances. However, it is a good guide for sizing a split system.

There a few things to be aware of when choosing the standard kW to use when calculating and you should use a higher value if:

  • You have a high ceiling.
  • The room is very sunny
  • Lots of windows
  • If your roof tiles and black or have a tin roof
  • Lots of people in the same area
  • Area uses lots of appliances
  • Ceiling insulation rating

The Importance of Choosing the Right Size Air Con

With the right size of an air conditioner, you increase the efficiency of this technology. A correctly sized air conditioner is supposed to cool down the temperature of your home slowly.

If the unit is too big, the unit will cool your room very quickly and then shut off. The problem is the furniture, ceiling, walls etc. haven’t had time to cool down. This results in the AC turning on and off running for short periods of time. This process increases the cost of cooling the room quite dramatically.

If the unit is too small, it simply won’t be able to cool the room to your desired temperature. In addition, it is always running at full power and this will reduce the lifespan of the air conditioning unit.

Most modern units are inverters and can reduce the amount of power used without switching off in cycles. With that being said it is advised to go larger than smaller if it is in your budget.

Air Conditioning Size Calculator 

There are a few ways to calculate the size air conditioner needed. challenge to calculate for the size of your air conditioner, there are ways on how you can do the math. You can use a formula, an online calculator, or a professional who can visit calculate for you.


This calculator is only indicative and other factors mentioned earlier, such as the height of your ceiling and your house features effect the power needed for your unit. 

Quality air conditioners are a great way to get comfortable at home during summer. However, a lot of buyers are being challenged when it comes to choosing the right size air conditioners they should buy for their home. So, we hope this article has helped. If not, or you have any concerns, get in touch and we can advise what size unit we would recommend based on your house.