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Determining the Right Size BTU or Ton Air Conditioner Required Per Square Feet of Space

The following table provides a guide for choosing the right size air conditioner based on the area needing to be cooled. The Air conditioner output and capacity is measured in BTU per hour. This chart includes areas from 100 square feet up to 2,500 square feet for comparison.

Area To Be Cooled (square feet) Capacity Needed (BTUs per hour)
100 up to 150 5,000
150 up to 250 6,000
250 up to 300 7,000
300 up to 350 8,000
350 up to 400 9,000
400 up to 450 10,000
450 up to 550 12,000
550 up to 700 14,000
700 up to 1,000 18,000
1,000 up to 1,200 21,000
1,200 up to 1,400 23,000
1,400 up to 1,500 24,000
1,500 up to 2,000 30,000
2,000 up to 2,500 34,000

Additional Considerations

  • If the room is heavily shaded, reduce capacity by 10 percent.
  • If the room is very sunny, increase capacity by 10 percent.
  • If more than two people regularly occupy the room, add 600 BTUs for each additional person.
  • If the unit is used in a kitchen, increase capacity by 4,000 BTUs.
  • Consider where you install the unit. If you are mounting an air conditioner near the corner of a room, look for a unit that can send the airflow in the right direction.

Measuring for Central Air Conditioning Systems in Tons

The basic formula for determining the required tonnage of a central air conditioning system is as follows:

( ( House square footage times 30 then divided by 12,000 ) – 1.0 ) = Required Tonnage

If you live in an area that has higher temperatures during the summer (such as 110 degrees in the desert) then don’t subtract 1 in the formula above.

To determine a more accurate size for your region, use the chart below.


Sources (as of 11 May 2017):

By Greg Johnson

Greg Johnson is a freelance writer and tech consultant in Iowa City. He is also the founder and Director of the ResourcesForLife.com website. Learn more at AboutGregJohnson.com

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