Bathroom Exhaust Fan Size Calculator

Just remember that the fan needs airflow to do its job.

Ceiling fan film. Duct length is calculated with the same formulas used to develop 2015 irc table m15062 and 2018 irc table m15042 ie the darcy weisbach colebrook equations. Press calculate minimum suggested bath fan cfm. 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.

Otherwise use the appropriate calculation based on the room size. Enter bathroom width ft. Toilet 50 cfm shower stall 50 cfm whirlpool 100 cfm 200cfm bathroom exhaust fan.

If your bathroom has a toilet or shower area enclosed by a door its a good idea to install a separate exhaust fan for that area. Cubic volume75 cfm necessary. Suggested cfm for the bathroom is based on cycling all the air in the bathroom 8 times per hour.

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. Why you need to have the proper size extractor fan. If the enclosed space is small a 50 cfm fan should suffice.

The formula to calculate bathroom exhaust fan size reads as follows. When installing a vent fan make sure theres at least a 12 gap under the bathroom door to allow fresh air to enter the room when the fan is running. This tool may be used to comply with the requirements of 2015 irc section m15062 and 2018 irc section m15042.

Bathroom extractor fans are mandatory in any bathroom without a window and still highly recommended in bathroom with windows. The bath fan calculator is standard guide to help you find the minimum fan rating for your specific bathroom. Calculate the floor area of your bathroom.

A second fan may be needed. For a rectangular bathroom this is done by multiplying the width and length. Enter bathroom length ft.