Many ceiling fan size charts are available at EnergyStar.gov, outlining the basic recommendations for ceiling fan size based on room size. Choosing the proper size of fan for your room ensures the most efficient air flow. A larger fan is not always the best choice for efficacy of cooling.
Another important feature of a ceiling fan is its CFM, or cubic feet per minute, rating. This rating is required by the Environmental Protection Agency and is a helpful tool in determining fan efficiency. Specifically, the CFM signifies the airflow of a fan on high speed. The higher the CFM, the more efficiently the fan will cool the room.