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Each year due to global warming, the summers are getting hotter and hotter. If you are losing your sleep because of the heat at night and thinking of having an air conditioner installed in your house to ease the problem, then knowing, how to calculate air conditioner (A/C) size can be handy. In fact, it is essential that you know how to do it. It will help you in determining air conditioner size required for your house and will give you a rough estimate about the capacity of the air conditioner to purchase. The following is a brief note on how you can calculate air conditioner size on your own.

How to Calculate Air Conditioner Size?

The task of sizing air conditioners is a matter of the application of the science rather than the art. You can use an on-line air conditioner size calculator to determine the size of the air conditioner that can make your home a hospitable place to live in, in the hot and humid summer. A properly sized air conditioner can work efficiently and help you realize your investment. On the other hand, under-sized air conditioners will run continuously, without cooling your house and without providing succor and worth. The over-sized air conditioner will not work more efficiently than the properly sized one. It is up to you to decide whether to install one of the portable air conditioners or the best central air conditioner available in the market.

The following are some tips, which may help you calculate air conditioner size:

  1. The first task in air conditioner sizing is to measure (in meters) the length and the width of each of the rooms in your house that you plan to cool with the air conditioner.
  2. The height of the room does not play any role in this calculation, because the cool air is heavy and sinks toward the ground.
  3. Find the area of each room you are interested in by multiplying its length and width.
  4. By adding together the areas of all the rooms you are interested in, you will arrive at the total area in your house to be cooled with the help of air conditioner.
  5. Multiply the total area by 337 BTUs and the product will give you the amount of heat, an air conditioner will have to remove from your house, in order to cool it.

Air Conditioner Size Calculator Chart for Single Room

Room Size (Sq Ft)

Recommended BTUs

0-150 5,000
150-200 6,000
250-300 8,000
300-350 10,000
350-400 12,000
400-450 14,000
450-500 15,000
500-600 18,000
600-700 20,000
700-800 22,000
800-900 25,000

The term BTUs stands for British thermal units.

Wait, your task is not over, yet. There are a few more calculations you have to do, in order to calculate the air conditioner size for your house. Calculate the area of each of your south side windows (width times height). Total the area of the windows and multiply it by 871 BTUs. This will give you the amount of heat entering your house through the south side windows. Calculate the area of each north side window, add them up and calculate the amount of heat entering your house through the north side windows by multiplying the total by 166 BTUs.Multiply the number of people by 400 BTUs, the amount of heat generated by each person per hour.