Some general guides are as follows:
- For an area 4x4m a 48” (122cm) fan. E.g. smaller bedroom/office
- For an area 5x5m a 52” (132cm) fan. E.g. common living area/ large bedroom
- For an area 6x6m a 60” (142cm) fan. E.g. large living area/ outdoors
Even though you might have a smaller room putting a larger ceiling fan might have some benefits to it. For example if you put a 52” fan in an area of 4x4 metre it mean you can run your fan on a lower speed and get the same amount of airflow.
However a bigger fan in a smaller room sometimes can look overwhelming. Darker coloured fans such as wooden finish, silvers and black can make the fan look heavy in a smaller room even in a larger room. Keeping to lighter colours such as pine, white, off-white can make the fan seem smaller even with a larger blade.
Ceiling height is also a factor, standard ceiling height is 2.1-2.7m. To install a fan in this height range is going to have little or no effect on the amount of airflow you will obtain. When you start going above that height range you want to be thinking about adding an extension rod onto your fan. Dropping it down to a standard height will give you more airflow and more efficiency.