You can calculate manually or using the CFM calculator below. You can read an insightful article about how to determine how many CFM bathroom exhaust fan you need given bathroom size here, but here’s the short and easy rule to follow: 1 CFM per sq ft. That means that if you have a...
When we change the design CFM to 60 we see that with a 3" duct this fan WILL NOT WORK period. When we then change the DUCT DIAMETER to 5 inches, the calculator says yeah, you're good, no limit. Watch out: using these fan calculators you can quickly get in trouble: that means hav...