Measure the length and width of the room in feet. Multiply the length by the width to calculate the square footage of the room.
Choose a fan that has a blade span of 29 inches to 36 inches if your room is no larger than 75 square feet.
Choose a fan that has a blade span of 36 inches to 42 inches if your room is at least 76 square feet but no larger than 144 square feet.
Choose a fan that has a blade span of 44 inches if your room is at least 144 square feet but no larger than 225 square feet.
Choose a fan that has a blade span of 50 inches to 54 inches if your room is at least 225 square feet but no larger than 400 square feet.
Use a standard downrod mount if your room has a standard ceiling height of about 10 feet. Standard downrod mounts lower the fan roughly 3 to 5 inches from the ceiling and are typically 1/2 inch or 3/4 inch in diameter.
Use an extended downrod mount if your room has an above-average ceiling height -- about 10 feet. Extended downrod mounts lower the fan anywhere from 5 inches to 120 inches from the ceiling. Your fan should hang about 8 or 9 feet off the floor.
Use a flush mount, with no downrod, if your room has a ceiling height of 8 feet or lower so that the fan would hang too low with a downrod.
Use a slope mount when mounting a fan on a vaulted or angled ceiling.