What is CFM in HVAC (The BEST Answer!)

The ‘V’ in HVAC stands for ventilation. This is because an HVAC always keeps moving air while cooling or heating. And CFM is an acronym for Cubic Feet per Minute. It is the measurement that helps technicians to map the airflow in a room.  Hot and cold air move around in the house and we have to find a system that can offer the desired comfort. CFM will help us with this.


The airflow measurement determines the size of the HVAC system and motor that a building needs for making it comfortable inside. The interior of the building will not become comfortably warm or cool if the HVAC system is not big enough. But a lot of energy will also be wasted if a bigger-than-required size HVAC system is installed in a building. This is why the calculation of CFM in HVAC is crucial. 

The relevance of CFM signify in HVAC

When you plan to buy an HVAC system, the first question that comes into mind is how to be sure of which is the best AC for your home. Because other than buying a model for its look or features, the most important thing is getting the correct size. Here, the CFM or Cubic Feet per Minute comes into play.

So if CFM HVAC has to be defined, it is the airflow calculation measured in Cubic Feet per Minute. The measured CFM determines the size of the HVAC you need to buy. For instance, you should get a 3-tonne HVAC system if the CFM is 1,200. 

Calculating the CFM

You obviously would like your home to have a good IAQ or Indoor Air Quality. That is why you need to measure the CFM before buying an HVAC. There is an online HVAC CFM calculator which can tell you how many CFM you need. Here, you will gain a general idea of how to calculate CFM in HVAC. 

An HVAC of 1.0 tonne requires 350-400 CFM. CFM also determines the heating capacity of the machine. Additionally, how much CFM you need for a room also depends on its size and the ACH (Air Changes Per Hour) you want the room to have. So it also determines the ACH.

The formula for calculating CFM is :

                                                     Area x Height x ACH / 60

The 60 here are 60 minutes. The size of the room has a big impact on the CFM. The bigger the room, the stronger your system has to be.

Professionals have special devices to measure this. This makes it easy to find out what the required CFM is for your house.

How to calculate CFM per square foot

We have to know the CFM per square foot to get an idea of what system we need to get for our house.

The CFM is an indicator of how much air the fan of HVAC moves. This has a connection with the ‘V’ or ventilation of an HVAC system. You need to have the following three pieces of information before deducing the CFM per square foot:

  • The CFM blower’s rating (probably 350 to 400 CFM per tonne): this is how strong the motor is
  • The HVAC system’s size (available in 1.5 – 5 tonnes)
  • Size of the area in which the HVAC system will provide its service to

Now, the equation to calculate the CFM per square foot using this information is:

                       Tonnage x CFM of the blower / Number of square feet

This equation can help you determine how many CFM a room having a certain square foot would receive. 

Why should you calculate CFM accurately?

Most systems mention the CFM on their spec sheet. This will make sure that you look at the right devices. If you don’t want to calculate CFM yourself, you can hire a technician to do this for you. If you bring your floorplan to a specialized store, they should be able to help you out as well.

If you think that you will not be able to determine your home’s CFM, you should call an experienced HVAC dealer. They will estimate the appropriate system capacity which would be right for you. While calculating the airflow, technicians use automatic calculation programs and charts which help them. The dealer will take into account the climate you live in, how many windows there are, and how warm or cool your family likes the temperature to be. They will also be able to suggest which HVAC system best suits your requirement, and will also consume less electricity (more energy-saving).

When you are about to choose an HVAC system for your home, it is important to keep the CFM in mind. You have to consider your needs and the space which will get the service of the HVAC system. It is important to calculate the CFM accurately. The system will not perform satisfactorily if the airflow is too less or too much. This can affect the system’s performance, and as a result, the components of the system can get damaged too.

By now you are aware that CFM is the measurement of the airflow’s volume. The cubic feet of air that goes by a fixed point per minute. The air circulation is more in a large space. This is because the air gets more space to move around. Therefore, if your home has a larger space, it has a higher CFM too. 

If the heater or AC is underpowered, your HVAC system will not condition your home as you want it to. The machine will struggle to function properly. Again, if the system is overpowered, your HVAC will not complete an entire heating or cooling cycle. Instead, it will rapidly switch on and off. This is called short cycling. 


Accurate estimation of CFM is very important to get the best HVAC for your living space. Buying a system with inadequate or even too much capacity can pose several problems. Either can wear away the HVAC system quickly and affect the system performance. And if you end up buying an HVAC system with an incorrectly calculated CFM, you will have to put up with a faulty functioning machine for about ten to fifteen years! The only other option you will have is to replace it. Replacing an HVAC system prematurely is not a very budget-friendly option for most people. 

Most of us use an air conditioner but are unaware of how it works or its different parts. But when we plan to buy an HVAC for our homes, there are certain facts that we should know about it. To stop the HVAC from malfunctioning, we must know that a regular maintenance plan is beneficial. Experts should come and do an annual check-up of the air conditioning and heating system. A regular check-up will keep the HVAC functioning efficiently for a long time.