Divide the volume of your bathroom in feet by 7 5.
Bathroom fan cfm calculator.
This is how often your extractor fan should be able to replace the bathroom with fresh air.
The cfm represents the airflow required to completely exchange the air in your bathroom 8 times in one hour.
That s why we developed this handy bathroom vent fan cfm calculator.
For example if your bathroom is 6 feet wide and 9 feet long its square footage is 54.
Continue shopping bath exhaust fans to find a right fan for your budget size and style.
Calculate how many cfm your bathroom fan needs by dividing the number from the step 2 by 7 5.
Coming in at 115 cfm the broan l100mg ventilation fan.
Use our handy online calculator to see what size vent fan you need for your home.
To arrive at your required cfm simply divide your bathroom s volume by 7 5.
To determine the square footage of your bathroom multiply the length times the width.
The rule of thumb is that you need at least 1 cfm per square foot of room area.
The result is the cfm or cubic feet per minute rating required for your bathroom fan.
This tool may be used to comply with the requirements of 2015 irc section m1506 2 and 2018 irc section m1504 2.
Suggested cfm for the bathroom is based on cycling all the air in the bathroom 8 times per hour.
So for an 80 square foot bathroom with a 10 foot ceiling you ll get the best results from a fan with a rating of at least 112 cfm.
Determine the required cfm for your bathroom fan.
More on this below.
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.
Static pressure in w g air flow cfm design conditions.
For standard square or rectangular bathrooms you can use the formula length x width x height volume.
So if your bathroom is 8 10 sq ft you need a vent fan with 80 cfms.
X cfm y in w g.
In any size bathroom there needs to be a vent fan with minimum of 50 cfm.
Duct length is calculated with the same formulas used to develop 2015 irc table m1506 2 and 2018 irc table m1504 2 i e the darcy weisbach colebrook.
Building code does not specify bathroom vent locations but in any size bathroom it is the most logical to install it over or as close as possible to the plumbing fixture that requires it.
Other options for bath fans include lights heaters and even humidity sensors.
An effective bathroom fan should be capable of replacing the entire volume of air 8 times per hour or every 7 5 minutes.
The higher the bath fan rating the more air can be vented out of the bathroom which means less moisture and mold build up.
Standard fan sizing applies to bathrooms that are 100 square feet or less.
