Home Improvement Expert Danny Lipford

Bathroom Vent Fan CFM Calculator


Installing a bathroom vent fan.

Bathroom vent fans serve an important function by removing humid air from your home to prevent mold and mildew from forming. Vent fans are rated by the number of cubic feet of air they move per minute (CFM), and it’s important to buy a large enough fan for the size of your bathroom.

Use our handy online calculator to see what size vent fan you need for your home. Simply enter the dimensions of your bathroom in the calculator below to determine the minimum size vent fan you need for the bathroom in your home.

When installing a vent fan, make sure there’s at least a 1/2″ gap under the bathroom door to allow fresh air to enter the room when the fan is running. Run the fan for 15 to 20 minutes after showering or bathing to expel all the excess moisture.

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Room Height

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3 Comments on “Bathroom Vent Fan CFM Calculator”

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  1. Leo Says:
    September 17th, 2014 at 7:34 pm

    Can I cause a problem with too large a CFM rating. Ex: If 68 CFM is what I need would one at 110 CFM be ok?

  2. Kirk Says:
    September 25th, 2014 at 8:35 pm

    Not a problem, fan will pull out excess stale air from the surrouding areas.

  3. Kirk Says:
    September 25th, 2014 at 8:41 pm

    Slightly open a nearby window to avoid negative pressure. Great for your home.

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