Minimum ventilation (CFM) required:

  • Bathroom size less than 50 Square Feet: 50CFM
  • Bathroom size more than 50 Square Feet:  1.1 CFM per square foot of floor space
  • For Example. 
    • If your room floor size is 45 square feet, you need buy 50CFM size ventilation fan.
    • If your room floor size is 60 square feet, so 1.1CFM x 60=66CFM, you need buy bigger size close to 66CFM, so it is 70CFM size is good for your room.