How to Calculate Air Conditioning Tonnage & Wattage

The output of an air conditioning system is measured in tons, which means the amount of energy required each hour to make one ton of ice in a period of 24 hours. Before installing an air conditioning system, the correct tonnage must be calculated to ensure proper ventilation and cooling for the area.

Before installing an air conditioning system, ensure the correct calculations are used.
  1. Take measurements of the area to be cooled. Multiply the length, width and height of the area in foot measurements to arrive at the total area.

  2. Divide the total area by 1000. The resulting number is your ton capacity.

  3. Multiply your final tonnage by 3517 watts to find the wattage for your air conditioner.


  • This calculation is a base figure. To properly ensure correct cooling, you must consider factors outside of the area. The number of windows, amount of light and any appliances can affect the overall cooling ability of an air conditioner.
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