Cubic Feet Per Minute (CFMs)

Make sure to measure the depth of your ceiling before ordering. The Home Ventilation Institute (HVI) recommends the air in your bathroom should be changed or moved eight times per hour. The amount of air changed or moved per cubic feet per minute (CFM) is based on your bathroom’s square footage.

To determine the size of the ventilation fan, use the following guidelines for bathroom ventilation.

50 CFM

For bathrooms smaller than 50 square feet, a 50 CFM fan is recommended.

1 CFM/ft²

For bathrooms 51 to 100 square feet in area, an exhaust fan should provide 1 cfm per square foot. For example: an 8-foot-by-10-foot bathroom has an area of 80 feet, so it should have a 80-CFM fan.

Add Up Fixtures

For bathrooms greater than 100 square feet, ventilation is based on the number and type of fixtures present; the following fixtures require the minimum CFM stated: toilet – 50 CFM; shower – 50 CFM; tub – 50 CFM; jetted tub – 100 CFM.


Installing the right size fan is essential to maximizing the fan’s performance. Improperly sizing your fan – installing a fan that is too small for the bathroom – will put “stress” on the fan and shorten its life and performance. Bathrooms over 9 feet may need to be sized up to the next CFM level.

What are SONES?

Bathroom fan sound levels are measured in SONES. Simply put, a sone is a unit of loudness and measures how you sense loudness. Your refrigerator operates at 1.0 sones and the sound of your television is 4.0 sones. The lower the sones, the quieter the room. AeroPure quiet bathroom exhaust fans operate at a range from less than 0.3 to 2.0 sones.

Fans so quiet you may not even realize they are on. We know from our fans that a little white noise is a good thing.