What size fan do I need for my bathroom?

Ventilation rates based on 8 air variations per hour are generally suggested. For most bathrooms, this works in a CFM bath area per square metre. For example, a 7 x 10 bath would require a CFM 70 fan. A CFM 50 rating is recommended as a minimum for 50 m2.Depending on the number of air changes per hour, rates are suggested. It works out to one CFM per square foot for most bathroom areas. A 7' x 10' bathroom would require a 70 CFM fan. The minimum rating for bathrooms is 50 sq.