What size exhaust fan should we use in our small (5’ x 7’) bathroom? –Tam

Hi Tam,

Bathroom vent fans are rated by the cubic feet per minute (CFM) of air they move and should be sized to replace the air in the room at least eight times an hour. If your bathroom has an 8’ ceiling, the CFM rating for your fan should be as least as high as the number of square feet (5’ x 7’ = 35 sq. ft.) in the room. So in your case, a 50 CFM fan should work. A bathroom with a higher ceiling would require a larger fan.

To remove more moisture from the air when showering, use a bit larger fan (80-110 CFM). Also, be sure there is at least a 5/8” gap under the bathroom door to allow fresh air to enter the room when the door is closed.

If your bathroom has a higher ceiling, multiply the width x length x height of the room, divide by 60 (minutes in an hour) then multiply by 8 (number of air exchanges per hour). For example, a 10′ wide by 15′ long bathroom with a 10′ ceiling would need:

10x15x10 = 1500
1500 ÷ 60 = 25
25×8 = 200 CFM rated vent fan

Or use our online bathroom vent fan calculator.

Good luck with your project,


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Danny Lipford

Danny Lipford


Danny Lipford is a home improvement expert and television personality who started his remodeling business, Lipford Construction, at the age of 21 in Mobile, Alabama. He gained national recognition as the host of the nationally syndicated television show, Today's Homeowner with Danny Lipford, which started as a small cable show in Mobile. Danny's expertise in home improvement has also led him to be a contributor to popular magazines and websites and the go-to source for advice on everything related to the home. He has made over 200 national television appearances and served as the home improvement expert for CBS's The Early Show and The Weather Channel for over a decade. Danny is also the founder of 3 Echoes Content Studio, TodaysHomeowner.com, and Checking In With Chelsea, a décor and lifestyle blog.

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