Calculating the size of a commercial air conditioner can be a complex business. There are books and software created for just this purpose, as well as calculators that consider multiple factors. For example, a building with a 12-foot ceiling is going to have different cooling needs than a building with a 9-foot ceiling. Also, a commercial kitchen will need more cooling power than a retail space. However, one general method for calculating commercial air conditioner size is based on the square footage of the area that needs to be cooled.

Things You Will Need
  • Measuring tape

  • Pencil and paper

  • Calculator

Measure the length and width in feet of the building or room, and multiply the two numbers to get the square footage of the area you want to cool.

Divide the square footage by 500. Take that number and multiply it by 12,000 to get the total BTUs you need to cool the space itself. For example, a 10,000-square-foot space divided by 500 equals 20. Multiply 20 by 12,000 to get 240,000 BTUs.

Add 380 BTU for each person who will be in the space while it is being cooled. Use an approximate number if the amount will vary.

Add 1,200 BTU for each kitchen in the space.

Purchase a commercial air conditioning unit with the capacity in BTUs closest to the figure you have calculated.


If the space you are cooling is poorly insulated or receives a great deal of direct sunlight, you may want to purchase a larger unit to counteract these factors. Also remember that you can choose to cool different areas of the space differently. For example, if you have a warehouse space and an office space, you might want to cool the office more effectively than a warehouse that is exposed to the outdoor climate all day.