Bathroom Fan Cfm Calculator

Calculate how many cfm your bathroom fan needs by dividing the number from the step 2 by 7 5.

Bathroom fan cfm calculator.

The cfm represents the airflow required to completely exchange the air in your bathroom 8 times in one hour. To determine the square footage of your bathroom multiply the length times the width. The result is the cfm or cubic feet per minute rating required for your bathroom fan. Divide the volume of your bathroom in feet by 7 5.

For standard square or rectangular bathrooms you can use the formula length x width x height volume. This tool may be used to comply with the requirements of 2015 irc section m1506 2 and 2018 irc section m1504 2. In any size bathroom there needs to be a vent fan with minimum of 50 cfm. Static pressure in w g air flow cfm design conditions.

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. More on this below. 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. Suggested cfm for the bathroom is based on cycling all the air in the bathroom 8 times per hour.

For example if your bathroom is 6 feet wide and 9 feet long its square footage is 54. Use our handy online calculator to see what size vent fan you need for your home. Determine the required cfm for your bathroom fan. 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.

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. According to the home ventilating institute you need to have one cfm per square foot of bathroom area. Standard fan sizing applies to bathrooms that are 100 square feet or less. That s why we developed this handy bathroom vent fan cfm calculator.

So if your bathroom is 8 10 sq ft you need a vent fan with 80 cfms. Continue shopping bath exhaust fans to find a right fan for your budget size and style. The rule of thumb is that you need at least 1 cfm per square foot of room area. The higher the bath fan rating the more air can be vented out of the bathroom which means less moisture and mold build up.

The bath fan calculator is standard guide to help you find the minimum fan rating for your specific bathroom. Coming in at 115 cfm the broan l100mg ventilation fan. An effective bathroom fan should be capable of replacing the entire volume of air 8 times per hour or every 7 5 minutes. X cfm y in w g.

To arrive at your required cfm simply divide your bathroom s volume by 7 5.