Bathroom Exhaust Fan Sizing Excel Sheet (CFM Calculator)

Free excel sheet calculator for sizing toilet and kitchen exhaust fan, this spreadsheet will help you calculate the ventilation air flow rate in CFM for the air extraction fan from toilet area. It depends on many parameters such as space area, space height and air change per hour ACH for the space type.

Download also: Fresh Air Calculator for AHU Working with VAV System and also Fan Static Head Calculator Excel Sheet

Bathroom Exhaust Fan Sizing

Ventilation Exhaust Fan CFM Calculation Formula:

Air Flow (CFM) = (Volume of Space) * ACH / (1.7)

• CFM= Cubic Feet/Minute
• Volume of space = area * height
• ACH= Air Change Per Hour, it is obtained from ASHRAE 62.1 table 6-4 and table 6-1
• Dividing by 1.7 is to convert from CMH (Cubic meter per hour) to CFM (Cubic Feet per minute)

Download Bathroom Exhaust Fan CFM Calculator

How many CFM do I need for my Bathroom Exhaust Fan?

to answer this question, follow these steps:

1. First download the above free excel sheet calculator. 
2. Measure the bathroom dimension (width-length-height).
3. Determine the ACH air change per hour (it is 10 ACH for toilets)
4. Fill the excel sheet with the above input data.
5. And you will get the CFM capacity for the exhaust fan.