A room smaller than 75 square feet can be effectively cooled with a fan only 29 to 36 inches.
Bedroom, Kitchen or Dining Room
A room that is 76 to 144 square feet needs a ceiling fan that is 36 to 42 inches in size.
Rooms that are 145 to 225 square feet require a ceiling fan that is 44 to 50 inches.
Rooms that are 226 to 400 square feet require a 50 to 54 inch ceiling fan. If the room is bigger than 400 square feet, divide it into two equal sections and get two fans.
Ceiling fans come in an array of styles and functionality. They can have lights, be reversible to send warm air back down into the room in winter and even come with remote controls. Most ceiling fans come with standard mounting kits. In a high ceiling room you need an extension rod. If the room has a angled ceiling, you needed a sloped mount. In low ceiling rooms, a flush mount ceiling fan is necessary.