What Size Air Conditioner Do I Need

size of air conditioning unit

How do I calculate what size air conditioner I need? | Split system air conditioning size calculator | Ducted air conditioner size calculator | Window & wall box air conditioning size calculator | How to calculate air conditioner size? | Air conditioner size for home | Air conditioner size for office | Air conditioner size for shop

Looking for the right air conditioner, but don’t know is it’s the right fit for you?

It can be a struggle to find the perfect air conditioner for your intended area, and can be even worse if you don’t know what your rooms measurements, potential capacity, and cooling load are. Not sure what air conditioner you need for your space? Well you have come to the right place! 

In order to find the ideal air conditioner for your space, you need to scale in all the factors including the size of your wall, room, type of system you want, if there are any windows in close proximity, the residency it’s being installed to, and the performance calculations of the air conditioning. Air conditioning can play a large factor in home comfort and individual wellbeing, as well as bringing value to any residency installed. 

How do I Calculate What Size Air Conditioner I Need?

When it comes to air conditioners, size matters the most and every room is different. It depends a lot on the rooms in your house and the overall area that they will be heating and cooling. Performance for each air-con varies on a lot of factors, but overall everyone needs the same thing. We made a simple table to help you figure out the average required capacity depending on the average room size. We give you this data in order to help you make the right choice and pick the unit of a split system that will fit your preference. 

Room Size for Air Conditioner Air Con Capacity
10m2 to 25m2 2.5 kW
25m2 to 35m2 3.5 kW
35m2 to 60m2 5-6 kW
60m2 to 85m2 7-8.5 kW
85m2 to 95m2 9-9.4 kW
Room size to Air Conditioner size & power

Split System Air Conditioning Size Calculator

Most of this information can be found on any brand air conditioning unit website but you can use our table above to get the estimates for your room. For example, room sizes up to 25-metre square benefit the most from 2.5 kW air conditioners and a simple rule of thumb, anything above 35m2 goes more or less the same in kW, example would be 35m2 into 3.5 kW, 60m2 into 6kW air conditioners etc. All rooms are not the same so keep that in mind and talk to an expert before buying.

Ducted Air Conditioner Size Calculator

When it comes to the ducted system you need to keep in mind that the power bill will be much higher and you need adequate roof space for the ducts themselves. Start off by calculating your total floor space, then multiply the entire number by your average ceiling height. The total floor area then needs to be multiplied by 160 watts. 

The number you get is the total watts air conditioner you need for your house and all the rooms. Keep in mind, 1000 watts = 1 kW and always look for something in that range, but higher since only an expert will be able to calculate how much cooling capacity you actually need for the rooms in your house. 

Window & Wall Box Air Conditioning Size Calculator

The average kW range people follow for window and wall box air conditioners is very similar to the split system one. Rooms that are an average size of 25 m2 would need a 2.5 kW unit to properly cool or heat the area. You can check our table above for the entire system range estimates. Installation of these units is usually in kitchens so an expert is required to tell you the correct size that you will need. 

How to Calculate Air Conditioner Size?


It’s important to get a unit that fits your home, you can’t get a 5kW system to cover big areas of 90 m2. The easiest and simplest way would be to measure the room, multiple the length and width. Multiply the area by 160 watts and you will have the estimate of which size air conditioner you need for that room. 


There won’t be a guide that will be able to tell you the correct and total size as an expert would be able to. He will calculate everything step by step, take into consideration the climate, windows, factor in the ceilings overall height and only then will he be able to tell you what size you need.

Air Conditioner Size for Home

Multiply the total length and width of a room in your home. If that room has a ceiling of 2.4m high, multiple the total floor space by 150 watts. If it’s higher and is 2.7m then multiply it by 160 watts. If your ceiling is 3m high, multiply by 175 watts. Follow this simple guide and you will get the estimate.

Air Conditioner Size for Office

The size calculation for office areas works differently than for your homeroom. A 10m2 office space could need up to a 2.5kW size air conditioner. Offices are usually made of different material and rarely have insulation so bigger sized systems are required for heating and cooling.

Air Conditioner Size for Shop

The shop air con systems need to be bigger in size and depending on the type of shop that installation can cost you more money. Usually, a 20 square meter shop needs a 4kW unit to properly service the entire area. Shops are usually not insulated so any heating and cooling don’t stay in the room for too long.

The 3 Steps to Air Conditioning Success

Air conditioning can of great importance to new home ownership, businesses, or residencies in general that can cool down a room while elevating the space, that’s why it’s vital you find the one that perfect for your space. In order to find the air conditioner best for your space, just remember the 3 vital steps, calculating the room dimensions, understanding the unit system you want, and the ideal size of your air conditioner. 

Related Air Conditioning Resources

Air Conditioning Installation Quotes

Are you considering installing air conditioning or replacing your current system? With rising power costs, keeping a cap on your air conditioner’s operating costs is crucial, so go for an energy-efficient solution. Read more…

Air Conditioning

Air Conditioning Installer Call Out Fee

With rising power rates, keeping a cap on your air conditioning running expenses is critical, so select an energy-efficient model. Read more at Specifier.

Air Conditioning

Evaporative Cooling Cost

The cost of evaporative coolers is calculated by the volume of water that can potentially be evaporated, and you’ll have to pay for it. Read more…

Air Conditioning

What is a Tradie

A skilled manual worker in a specific trade or craft is known as a “Tradie” (trade specialist). Read more…

Air Conditioning