CFM per ton

How Many CFM Per Ton?

If you’re not an HVAC tech it can be difficult to know what size or tonnage system is needed for your home or desired space. The rule of thumb for cooling is 400 CFM per ton or 1 CFM per 0.2 tons.

Whether you’re installing a system in a new home for the first time or upgrading your home’s old system, it is important to be aware of how many square feet the space that you’re trying to cool is.

Residential Units

Residential air conditioner units come between one and five tons, which is sufficient enough to cool 400 to 2000 square feet respectively. You figure out what tonnage system you need by dividing the total square footage of the space by 400.

Having too many tons for the space or having too little tonnage to cool the space both have their drawbacks.

Excess Tonnage

One would think that having over the recommended amount of ton of cooling for their specific area could only be a good thing but when it comes to HVAC units this is not the case.

The problem with having excess tonnage is that it actually cools the air down faster than desired. This doesn’t give your HVAC system the time it needs to remove the humidity in the air. 

Excess humidity can cause general discomfort for the people in your home, as well as present legitimate health concerns in the form of mold and mildew growth. It can also cause your space to feel warmer than it actually is which can lead to the prolonged running of your system and higher energy costs.

Not Enough Tonnage

If your air conditioner’s tonnage is less than the preferred amount for the size of your space you can have issues as well.

What this does is causes your system to run constantly because it can’t keep up with the temperature outside. This leads to overall discomfort because your home is never going to reach the desired air temperature, it’s also a cause for higher than average energy bills.

Commercial Units

Commercial air conditioning units do come in larger tonnage sizes due to the as to be expected increased square footage. Commercial air conditioners can come in as many as 30-ton units.

The same rule of thumb can be applied to figuring out the required tonnage for a commercial unit that can be applied to residential units, which is that of 400 square feet per ton.


The important thing to remember when you are trying to figure out what tonnage system is appropriate for your desired space, be it residential or commercial, is that you can expect 1 ton to be able to cool up to 400 square foot of space.

This 400 square foot per ton of cooling needs to be near exact because having too much, or too little tonnage can cause increased energy bills, increased air temperature and discomfort, and even present genuine health concerns. If you have any questions do not hesitate to consult with a licensed HVAC technician in your area.