The cfm represents the airflow required to completely exchange the air in your bathroom 8 times in one hour.
Cfm for bath fan.
Press calculate minimum suggested bath fan cfm.
Standard fan sizing applies to bathrooms that are 100 square feet or less.
So if you have a bathroom that is 12 feet long 15 feet wide and 10 feet tall then it has a volume of 1800 cubic feet 12 x 15 x 10 and a cfm of 240.
A fan that s too small won t remove moisture and odors efficiently and will need to run longer increasing wear on the motor.
Standard fan sizing.
An effective bathroom fan should be capable of replacing the entire volume of air 8 times per hour or every 7 5 minutes.
Enter bathroom width ft.
Bathroom vent fans are rated for the amount of air they can move measured in cubic feet per minute or cfm.
The result is the cfm or cubic feet per minute rating required for your bathroom fan.
The rule of thumb is that you need at least 1 cfm per square foot of room area.
Enter bathroom length ft.
To arrive at your required cfm simply divide your bathroom s volume by 7 5.
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.
Enter bathroom height step 4.
Determine the required cfm for your bathroom fan.
A 50 square foot or smaller bathroom needs a 50 cfm fan.
Bathroom vent fans serve an important function by removing humid air from your home to prevent mold and mildew from forming.
Suggested cfm for the bathroom is based on cycling all the air in the bathroom 8 times per hour.
For example a bathroom with a volume of 1000 cubic feet 28 3 cubic meters needs a fan capable.