How Many CFM Is a Box Fan (With Highest CFM Box Fan)

20 inch box fan CFM ranges from 1800 CFM to 2500 CFM. The average box fan is 2300 CFM.

Full details on box fan CFM are available here.

A box fan is also called a window fan because that is where they are normally placed, exchanging cool outdoor air for stuffy air in your home. And 20 inch box fans are the most popular size from all leading brands including Lasko, Air King, Holmes, Amazon Basics and Hurricane.

How Many CFM is a Box Fan

Box fan CFM starts around 1800 cubic feet per minute (CFM). The highest CFM in a 20-inch box fan based on research covering all top brands is 2500 CFM, which provides a strong, consistent breeze.

That’s nearly 80% higher than the box fans considered low CFM, which is around 1400. That means if you’re trying to exchange air in a warm, stuffy room, the high CFM fan will do it almost twice as fast as the less efficient fan.

As you browse box fans information online, you’ll find that the average box fan has a CFM between 2200 and 2400 CFM.

Terminology tip: As noted, CFM stands for cubic feet per minute. It is a measurement of the volume of air that can be drawn through a fan every 60 seconds. A cubic foot is an amount of air 1 foot long, 1 foot wide and 1 foot high.

High CFM Box Fan

Lasko Lasko-20 Premium Box Fan
Lasko Lasko-20 Premium Box Fan, 2500 CFM

A fan is considered a high CFM box fan when it moves at least 2200 CFM. The highest CFM for box fans ranges from 2400 to 2500 CFM.

Best-selling Brands: The best Lasko box fan CFM is 2500. At the top of the list are fans like the Lasko 20 Premium fan. The CFM for the popular Lasko Power Plus box fan is just 2000, which is 20% lower than those with the top CFM ratings.

If you’re wondering about the rated CFM for Holmes box fans, our research shows two things. First, past Holmes models had CFM ratings of 1400 to 2000. Secondly, Holmes no longer makes standard 20 inch box fans. There are none shown on the Holmes site. And most listed on retail sites show that the units are no longer available.

If you’re in the market for a high CFM 20” box fan, here are top options.

Box Fan CFMSamplesFan Type
1800 CFMGenesis G20BOX-WHT20” Box Fan
2140 CFMAir King 972320” Box Fan
2300 CFMUtilitech FB50-16HB20” Box Fan
2400 CFMHurricane Box Fan & Amazon Basics 20” Box Fan
2500 CFMLasko Lasko-20 Premium Box 372320” Box Fan
3000 CFMNewAir 18-inch Wall Mounted Fan18” Wall Mounted Fan
4000 CFMTornado 18 Inch Wall Mounted Fan18” Wall Mounted Fan

Wall fans? The best CFM for box fans is 2500. But there is a demand for fans with greater airflow.

As a result, two wall mounted fans are included in the list. Of course, the issue with these fans is that it is hard to hang them in front of a fresh air source like a window or door. The NewAir unit is also available as a floor fan with its own frame and the same CFM. It can be placed in front of an open door or on a bench or table in front of a window to exchange air more effectively.  

Voltage: These are all 120V box fans. They plug into any standard outlet. The CFM for all 120V box fans ranges from around 1400 to 2500 CFM.


What type of fan moves the most air?

A ceiling fan moves the most air of any fan type found in most homes. The highest CFM fans in the “ceiling fan” niche move close to 10,000 CFM, though the most popular sizes and styles have CFM ratings of 3,500 to 6,000. All else being equal, the fans with the longest blades and the most blades have greater airflow capacity.

Wall-mounted and floor fans have the capacity to move around 2,250 to 4,000 CFM. That’s impressive airflow for these residential fans that are typically 18 inch fans.

Attic fans come in a wide range of CFM’s. Also called whole-house fans, they range in airflow from about 1,500 to 9,500 CFM.

Are 5 blade fans better than 3?

Yes, fans with 5 blades are better than fans with 3 blades if your concern is CFM airflow. That is considering that all else is the same – the fans are the same size, the blades are the same material and pitch, and the motors are moving at the same RPM.

When all else is equal but fan speed is different, the faster-spinning fan will have a higher CFM.

Fan CFM to room size?

A box fan exhausts stale room air and replaces it with fresh outside air. It should be rated to fully replace the entire volume of air in a few minutes.

Fans are rated in CFM or cubic feet per minute. So, it is important to know the cubic feet of a room. Cubic feet is the sum of room length x room width x room height.

A 20 x 24 living room with 10-foot ceilings (20x24x10) is 4,800 cubic feet. If you want the air exchanged every 3 minutes, which is typical, then divide 4,800 by 3, and you get 1,600. A 1,600 to 2,000 CFM box fan will nicely do the job.

Should a box fan face in or out?

It can be placed either way depending on how strong you want the breeze to be. 

First, a box fan should be placed in a window in line with prevailing winds. For example, consider a room with windows on the east and west, and the wind is coming from the west. Open windows on both sides for the best ventilation.

Diagram from the National Renewable Energy Lab

Now, if you want to feel a strong breeze, put the fan in a west window facing in. If you want milder air exchange, position the fan in an east window facing out.

Can a box fan help prevent Covid spread?

Possibly. Here is guidance from the US Environmental Protection Agency on ventilation, box fan use and Covid 19 prevention.

Written by

Rene has worked 10 years in the HVAC field and now is the Senior Comfort Specialist for PICKHVAC. He holds an HVAC associate degree and EPA & R-410A Certifications. Protection Status