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How to guide on sizing an Air Conditioner for any room.

There are very important factors to consider when sizing an air conditioner for a room.

Here are some simple steps to correctly size an air conditioner for almost any room.

Your first step is to measure the room size.

  1. Measure the length and width of the room in meters. (If you do not own a tape measure you can walk it out and get a rough estimate.)
  2. Calculate the total area by multiplying the length of the room by the width of the room.
  3. This amount is the total room size in square meters.

An air conditioners capacity / size is measured in BTU, now using the total room size you have worked out, we need to establish how many BTU’s we going to need to Cool or Heat the room.

For residential applications we use a base load of 450 – 550 BTUs per square meter.

  1. Take 450 BTU and multiply it by the total room size.

Example: 4 meters length x 4 meters Width = 16 square meters, multiplied by 450BTU = 7 200 BTU which means you will require a 9,000 BTU Air conditioner.

It is considered best practise to always round to the next available size.

  1. The most common residential Air conditioners are called Mid-Wall Split Air Conditioners. They typically come in the following sizes and cover these surface areas:



But there are some other things to also consider when sizing an Air Conditioner correctly.

  1. Ceiling Height, the calculation provided above assumes that we are working with a standard ceiling hight in South Africa which is between 2.1m and 2.4m
  2. Sunlight Exposure plays a massive role in sizing an air conditioner correctly, if you are getting a lot of sunlight in the room you would need to add another 15% onto our original BTU calculation.
  3. Occupancy, how many people are in the room? It is standard practise to add 600BTU per person to account for the heat load they produce.
  4. Appliances, also add heat into the equation as they produce warmth while in operation. (Computers, Tv’s, Lights)

We hope you found this information informative and useful.

Please feel free to contact us at for more information on this topic.

We do believe that size visits are always best practise to make 100% sure all factors are carefully considered.