A practical guide to air conditioner sizes

In the air conditioning world, “one size fits all” is definitely not something we can count on. As a matter of fact, determining the right size and capacity is the first step in choosing the perfect air conditioner for you to enjoy the comfort this summer.

Find out how to do the correct calculations!

Let’s talk a bit about common sizing mistakes, shall we? We’ve proved in the previous blog that bigger is not always better as oversized units will turn on and off increasing strain on the compressor, as well as on the energy bill. On the other hand, if you choose an air con that is too small for the intended space, it will work far too hard to do the job and eventually bring you the same result as in the first case.

So, in order to avoid these mistakes, we will guide you through a process that can help you understand the basis of air conditioner sizing. Let’s get started!

Methods to calculate the size and capacity:

1. Applying a formula

The first step in determining the correct capacity of an air con unit is to calculate the surface of the area you wish to cool. After doing this, you need to measure the ceiling height as this factor is also part of the formula we’ll unveil below:

Here are a few references, based on a room with an insulated roof and normal window sizes:

  • Ceiling height is 2.4 m

Surface area x 150 watts/sqm

  • Ceiling height is 2.7 m

Surface area x 160 watts/sqm

  • Ceiling height is 3 m

Surface area x 175 watts/sqm

For example, if you wish to cool a house having a surface area of 100 sqm and ceiling height of 2.7 m, then you multiply 100 by 160, which equals 16000 watts or 16 kW. This is the capacity you should look for at the AC.

Another way to find out the correct capacity is by looking at the chart below – provided by Canstar Blue – which takes into account individual parameters by room:

room size calculator

2. Using an online calculator

When you work with an online calculator, you may expect more accurate results than the ones from the previous method. In this case, however, you need to provide detailed information of your household.

Other factors to take into consideration:

  • Shady or sunny rooms
  • Type of wall and roof insulation (if applicable)
  • Number of inhabitants per room

The calculator created by AIRAH (Australian Institute of Refrigeration, Air Conditioning and Heating) can be a great tool to determine the air con capacity you need for your home.

Use the link below to get started:

Calculator Size

3. Asking for a qualified and professional advice

Undoubtedly the most precise method to learn about the correct size and capacity of the air conditioning system that best suits your lifestyle is talking to an expert.

Having years of professional experience and customer satisfaction in the background, the team at Jaric is ready to give you an accurate answer to your questions, as well as to solve any of your air conditioning problems you may encounter.

Call us now at 1300 452 742 and enjoy the Jaric Air Conditioning difference.

Until next time, stay cool and do the right calculations!

Your friend and AC expert,

John Ricca



Head Office 1300 452 742

64 McNeill Road
Kallangur QLD 4503
(07) 3910 2499
10 Tahoe Ct
Thornlands QLD 4164
(07) 3333 2425
6/95 Riverside Place
Morningside QLD 4170
(07) 3333 2627
Elanora (Gold Coast)
82 Silver Glade Drv
Elanora QLD 4221
(07) 5667 7266
18 Smith St
Capalaba QLD 4157
(07) 3333 2425
7 Dangar St
Belmont QLD 4153
(07) 3166 9355
We provide non-contact service & installations

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