Updated November 21, 2023
When searching for your next fan in your warehouse, factory, garage, office, barn or other building, it’s important to purchase a fan that is sized correctly for your space.
Investing in the best fan for your needs can help you economically cool the space for years to come. Among the many factors that determine the effectiveness of a fan (type of motor, size, etc), fan CFM is one of the most crucial.
Continue reading to learn more about the CFM fan requirements and how it can be a major key to finding the correct fan for your needs.
What Is CFM?
Cubic Feet per Minute - or CFM - determines the amount of air that a fan can move through a room while operating at the highest speed. The larger the space, the higher the fan CFM must be in order to efficiently cool a room.
CFM for fans is a critical measurement for determining the right fan for your space. If the CFM is too low, the room will be unable to be cooled and undermine any energy efficiency of the fan. Even running 24/7, the low CFM would cause the space to feel too warm.
View our Fan CFM Calculator ->
Factors That Affect Fan CFM
When it comes to the CFM for a fan, three factors have a significant impact:
Rotations Per Minute (RPM)
The Rotations Per Minute how many times the fan blades will make a 360-degree rotation every 60 seconds.
The size of the blade will determine how much air can be moved. The larger the blade, the greater the airflow.
The blade’s pitch plays a significant role in the amount of airflow. If the tilt is more aggressive, the amount of air moved through the room will increase.
The combination of these three factors will determine the fan’s CFM. If the RPM, blade size, and pitch are all large, the fan will move more air each minute and result in a higher CFM.
Evaluating CFM Ratings
CFM is always going to be specific to your application. A CFM rating that works for a warehouse may not be applicable to a barn. Your application will have a recommended amount of air exchanges per minute.
For example, a warehouse has a recommended range of about 4 to 10 minutes between exchanges. A barn ranges between 10 to 20.
Fan design will have a huge impact on a CFM rating. As mentioned above, the design of the fan blade will determine how much air can be moved. A blade that has a higher pitch usually moves more air than those with a lower pitch. The same is true for motor power and speed.
When getting a CFM rating, for some fan systems knowing the static pressure will be equally important. Static pressure refers to the resistance to airflow in ductwork.
For example, if your application requires an in-line duct fan, knowing what your static pressure is upfront will be helpful when figuring out what CFM is best for your space.
Room size & requirements
The size of your space will be the most important factor when considering how much CFM you need. To get an accurate CFM recommendation, you will need to know the length, width and height of the area to get the room volume. Once you have that information and how many air exchanges you would like to complete per minute, you are able to calculate the CFM needed for your application.
A garage that has dimensions of 25’ L x 30’ W x 20’ H and a frequency of 7 air exchanges will require at least 2,358 CFM. Depending on the size of your space, you may need multiple fans to feel the benefits of fresh air.
CFM Ratings for Various Fan Types
Bathroom Exhaust Fans
Bathroom exhaust fans usually move relatively lower CFM due to two factors:
- Bathrooms are typically smaller rooms and do not require a high CFM bathroom fan to be effective.
- Low noise is usually an important feature of bathroom fans and therefore lower a CFM rating is better.
Ceiling fans can put out an enormous amount of CFM, however, they are usually rated in Square Foot Coverage. A few things to consider when deciding on a ceiling fan with the right CFM:
- The ceiling height of your space that you intend to install your ceiling fan in is very important. The higher the ceiling, the larger the ceiling fan you will need.
- Ceiling fans are used for two purposes. First, to create a downdraft current of air from the ceiling to the floor and cause a cooling effect at ground level. Secondly, to destratify the hot top layer of air in a room, and help mix it more evenly so your space stays a more even temperature throughout.
- Due to the dual function of ceiling fans, CFM is usually not a rating that is used to help size the fans to your room. Instead, most ceiling fans, especially HVLS fans, are sized based on the square footage they can cover.
Ventilation fans are used to pull hot, stale or contaminated air out of your space. CFM is a very important rating for ventilation fans as direct air movement is their primary function.
- For wall and roof exhaust ventilation fans, the CFM output is directly related to the size of the fan blades, the pitch of the fan blades and the HP rating of the motor. Increase any of these factors and you are likely to have an increase in CFM.
- Many times, the selection of the right ventilation fan comes down to calculating the CFM you need to ventilate your space, and then finding the fan that fits within the space you have for installation.
How Much Fan CFM Do I Need?
When it comes to the CFM for fans in your commercial or residential space, the size of the room is the largest consideration. We have a CFM calculator that can help you determine the exact CFM required to cool your space.
However, a general guideline can be found below if you do not have the room’s exact dimensions at this time:
- Under 200 square feet: 2,000 to 3,000 CFM
- 200 to 300 square feet: 3,000 to 4,000 CFM (typically a standard bedroom or kitchen)
- 300 to 450 square feet: 4,000 to 6,000 CFM (usually a master bedroom or living room)
- Over 450 square feet: 5,000 to 9,000 CFM
Commercial spaces that have rooms far larger than 450 square feet should consider installing multiple fans in order to achieve the fan CFM required to keep guests cool.
Industrial Fans Direct Helps You Find the Fan CFM You Need
Industrial Fans Direct boasts one of the highest-quality inventories in the industry. Whether you have a specific fan style in mind or need to order in large quantities, our team is well-positioned to help you find a fan CFM to serve your exact needs.
What does CFM mean for fans?
CFM stands for the cubic feet per minute that is calculated by multiplying the velocity (feet per minute) with the area (square footage). Fans are then measured and rated for certain CFMs that can help meet requirements needed to cool down your space.
Is higher fan CFM better?
A higher CFM won’t always be better. You want to make sure that you are getting the right amount of CFM for your needs to gain optimal efficiency. If a fan has too much CFM for a room, you can cause draftiness and face increased energy costs.
How much CFM do I need to cool a room?
How much CFM you’ll need is directly related to the size of the room you are looking to cool down. For example, if you have a warehouse that is 25’ L x 50’ W x 75’ H, we would recommend somewhere between 14,000 to 15,000 CFM.
Does higher CFM mean quieter?
Typically, the higher the CFM rating the higher the noise level will be. Because these fans are built for commercial and industrial applications, they will often be a little noisier than fans found inside a house. Though if a fan has a lower RPM, it will usually put out less noise, and lower CFM, than those with a higher RPM.