Whether you’re moving into a new home, making updates to a current one, or building a home from scratch, one of the most important decisions you have to make is what air conditioning system to install.  

And, when choosing a system, one of the biggest factors in keeping your and your family comfortable is what size system to install.  

Below, our experts have some tips to help you choose the right size for your needs! 

Square Footage

One of the main deciding factors will be the square footage of the space you need to cool. Though, this isn’t as simple as it sounds. 

Square footage of your home, combined with heat gain/loss and environmental circumstances will provide a great thumbnail estimate for what size AC unit you need. However, there is a formal calculation called a “Manual J” that will take all inputs and give you the proper sizing. The only way to make the most accurate final decision is to have a Manual J performed. 

The table below outlines a guide for choosing the right size air conditioner based on square footage.  


Area being cooled, in Square Feet Capacity (in BTU’s) needed = square feet * 35
100 – 1503,500 – 5,250 BTU’s
150 – 2505,250 – 8,750 BTU’s
250 – 300 8,750 – 10,500 BTU’s
300 – 35010,500 – 12,250 BTU’s
350 – 40012,250 – 14,000 BTU’s
400 – 45014,000 – 15,750 BTU’s
450 – 55015,750 – 19,250 BTU’s
550 – 700 19,250 – 24,500 BTU’s
700 – 1,00024,500 – 35,000 BTU’s
1,000 – 1,20035,000 – 42,000 BTU’s
1,200 – 1,40042,000 – 49,000 BTU’s
1,400 – 1,50049,000 – 52,500 BTU’s
1,500 – 2,00052,500 – 70,000 BTU’s
2,000 – 2,500 — 2,000 * 35 = 70,00070,000 – 87,500 BTU’s


Factors Beyond Square Footage 

Square footage is one of – if not the – first factor to consider when picking an air conditioner size. However, there are some other factors beyond that to also take into consideration. Listed below are other things that could affect your choice of air conditioner size. 

  • If the room is heavily shaded or very sunny
  • How many people regularly occupy the room at one time
  • If the unit is used in a kitchen
  • 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.
  • The number, age, condition, orientation of windows – do your windows face south?

Any TemperaturePro technician can happily walk through all these factors and more in your home and help you diagnose what size air conditioner is right for you! 

Measuring In Tons for a Central Air Conditioning Unit 

In addition to everything mentioned above, there is a formula that can be used to determine the required tonnage of a central air conditioning system. We’ve copied this formula below for reference, however to ensure accuracy we advise that you have a TemperaturePro HVAC expert come out and assess the space for you! 

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

Additionally, the table and image below show a more accurate size based on what region of the country you live in:


Tons Zone North, Square FeetZone South, Square Feet
1.5 900 – 1,200 sf750  – 1,000 sf
1,200 – 1,500 sf1,000 – 1,250 sf
2.5 1,500 – 1,800 sf1,250 – 15,00 sf
31,800 – 2,100 sf 1,500 – 1,750 sf
3.521,000 – 2,400 sf1,750 – 2,000 sf
2,400 – 2,700 sf2,000 – 2,250 sf 

Deciding on the right size unit for your home can feel like a daunting task! It’s not cheap to replace or install a new unit, so you want to make sure you pick the right size for your needs. 

These tips should help you get started on the right path. Call your local TemperaturePro today to take the next step and have a technician help you determine the right size for you!