How to calculate AC tonnage for your projects

Summers setting in, and it’s time to bring out those AC’s, and a lot of us will be out looking for new AC’s this season.. Shopping for the right kind of air conditioner can be quite confusing, and a lot of times we can be misled into buying a larger unit than required or worse than that, buying something which is too small for our room!
It is important to have some idea about how to calculate the AC capacity that you require for your room… which depends not only on the size of the room but also on the size of the windows, which direction they face, number of people who occupy it, the insulation of the room (is it on the top floor or in the basement) even the wattage of equipment in the room influences the required AC capacity (more relevant for offices).

The most basic thumb rule to get started is to calculate the volume of your room in feet and divide it by 1000, this will give you the required capacity in TR (tons). So a 10 foot by 10 foot room which is 10 feet high will need a one ton AC (10’x10’x10’ = 1000 Cu.ft. / 1000 = 1 ton).

But to add some precision to this calculation do the following:

Measure the dimensions of your room.
Identify the orientation of your windows and measure their sizes (don’t add up the window sizes as a north facing window impacts the calculation different from a south facing window)

Follow the link below and use the AC tonnage calculator provided by companies like carrier to get a the required tonnage for your room (more calculators can be found online)

Link to calculator

After this let’s understand the units. One ton (TR) of refrigeration refers to the heat extraction capacity of the unit, it’s an American unit and equates to the amount of energy required to melt one short ton of ice (about 907 KG or 2000 pounds). This is equivalent to 12000 BTU/h (British thermal unit), beware of products that claim to be a one ton unit but have a cooling capacity of less than 12000 BTU. Finally we need to check the power consumed by the unit in watts and the star rating which is based on the EER (energy efficiency ratio). If we convert the cooling capacity to watts (1 ton = 12000 BTU = 3517 watts) and then divide it by the power consumed to achieve this we get the EER, the higher the better (this shouldn’t ever be below 2.3 and should be around 3.5 for a 5-star rating).

So to summarize:
Calculate the cooling capacity (in TR) based on your room requirements
Check the cooling capacity (in TONS as well as BTU then convert it to watts)
Check the power consumed.
Check the BEE rating. (verify by dividing cooling capacity by Power consumed)

Updates 6 feb 2019:

If you found the above article useful and are looking to go out and buy a new AC this season, here’s an update on the latest innovations in Air conditioning technology that you might want to look out for.

Cloud enabled AC control 

Imagine being able to turn your AC on 15 minutes before you reach home. AC’s with cloud control are here, these AC’s connect to the internet through the WiFi system of your home and are easily controllable through an app.

Please note: Cloud connectivity is different from WiFi connectivity, where appliances are controlled by devices within the Wifi network, the main difference being that a cloud based AC will allow you to control the AC from anywhere.

Check out brands like Lloyd and LG for options with this feature

Reverse cycle 

Here’s another innovation that’s been around for a few years but has been gaining traction recently. Reverse cycle AC’s come equipped with heat pumps so that you can convert your AC into a heater in the winter. These systems are perfectly suited for winters where the temperatures don’t fall below freezing. No more evenings spent huddling around the blower, this is an energy efficient way to keep your home nice and cozy.

Recommended brand for reverse cycle: Daikin

Do leave your questions and comments and if your looking for a home renovation visit us at to get a free estimate.