The size of the floor fan you need depends on the size of the room you intend to cool; a larger room typically requires a fan with a larger blade span and higher airflow capacity, often measured in cubic feet per minute (CFM). For medium to large rooms, a fan with a blade span of 20 inches or more and a CFM of at least 2,000 is generally recommended. Check our How to Choose the Right Sized Fan for more tips.