The short answer
A 14 by 12 ft room (168 sq ft) with an 8 ft ceiling needs a 44 to 50 inch ceiling fan, mounted flush. A small 10 by 8 ft room (80 sq ft) takes 36 to 42 inches. On a 12 ft ceiling, use a 24 inch downrod so the blades hang at about 9 ft.
Fan size and downrod chart
Blade span by room size, and the downrod that keeps the blades about 7 to 9 ft off the floor.
| Room | Blade span |
|---|---|
| Up to 75 sq ft | 29 to 36 in |
| 76 to 144 sq ft | 36 to 42 in |
| 145 to 225 sq ft | 44 to 50 in |
| 226 to 400 sq ft | 50 to 54 in |
| Over 400 sq ft | 56 in or larger, or two fans |
| Room | Sq ft | Span |
|---|---|---|
| 8×8 ft | 64 | 29–36 in |
| 10×10 ft | 100 | 36–42 in |
| 12×12 ft | 144 | 36–42 in |
| 14×14 ft | 196 | 44–50 in |
| 16×16 ft | 256 | 50–54 in |
| 20×20 ft | 400 | 50–54 in |
| Ceiling | Downrod | Blades at |
|---|---|---|
| 8 ft | Flush mount | 7 ft |
| 9 ft | 6 in | 7.5 ft |
| 10 ft | 12 in | 8 ft |
| 11 ft | 18 in | 8.5 ft |
| 12 ft | 24 in | 9 ft |
| 13 ft | 36 in | 9 ft |
| 14 ft | 48 in | 9 ft |
| 15 ft | 60 in | 9 ft |
| 16 ft | 72 in | 9 ft |
How it works
The formula
Fan makers use a simple chart: the bigger the room, the longer the blades. We apply it to your floor area, then pick the downrod from the ceiling height.
blade span = the range for that area (chart above)
two fans if length > 1.5 × width and area > 300 sq ft; each fan covers half the area
blade height = ceiling − (downrod + 12 in) ÷ 12
largest span = (shorter side × 12) − 2 × 18 in
Assumptions
- Blade span by room area is the common industry chart, also shown on ENERGY STAR and fan maker sites: up to 75 sq ft, 29 to 36 in; to 144, 36 to 42; to 225, 44 to 50; to 400, 50 to 54; bigger, 56 or larger. Standard fan sizes: 30, 36, 42, 44, 48, 52, 54, 56, 60 inches.
- Our rule for two fans in a long room: length more than 1.5 times the width and more than 300 sq ft. It is our rule of thumb. Each fan is sized for half of the area.
- Blades must hang at least 7 ft above the floor. Best is 8 to 9 ft. We assume the motor and blades hang 12 in below the end of the downrod.
- Downrod: flush mount for an 8 ft ceiling, then 6 in at 9 ft, 12 at 10, 18 at 11, 24 at 12, 36 at 13 and 48 at 14 ft, plus 12 in for each foot higher. We round down to whole feet.
- Keep blade tips at least 18 in from walls.
- Airflow: the label lists CFM and watts at each speed. The ENERGY STAR product list (energystar.gov) is a good place to compare. As a goal, look for about 100 CFM per watt or more at high speed. That number is our target, not an ENERGY STAR requirement.
Worked example: a 400 sq ft great room with a 9 ft ceiling
A room 25 ft long and 16 ft wide, ceiling 9 ft.
- Area: 25 × 16 = 400 sq ft.
- Shape: 25 is more than 1.5 × 16 = 24, and the area is over 300, so use 2 fans.
- Each fan covers 200 sq ft, which takes 44 to 50 in: 44 or 48 in.
- Downrod for 9 ft: 6 in. Blades at 9 − (6 + 12) ÷ 12 = 7.5 ft.
- Clearance: each fan has a 12.5 ft square, so the largest span is 12.5 × 12 − 2 × 18 = 114 in.
Too big or too small
- Too big: wobble and wind. A fan too large for the room blows papers around and can feel like a draft. Its blades may also come too close to walls.
- Too small: it can't move the air. A small fan in a big room only stirs the air right under it. You won't feel the breeze.
- Too low: a safety risk. Blades under 7 ft are a head hazard. Use a longer downrod on tall ceilings, and a hugger fan on low ones.
- Too high: weak breeze. A fan hanging near a tall ceiling pushes air at the ceiling instead of at people. A longer downrod brings it down to 8 to 9 ft.
- Between sizes? A bigger fan can run slower and quieter, and still move the same air. Take the larger size if the wall clearance works.
Questions people ask
What size ceiling fan do I need for my room?
Match the blade span to the room area. Up to 75 sq ft: 29 to 36 inches. 144 sq ft and under: 36 to 42. Up to 225: 44 to 50. Up to 400: 50 to 54. Larger rooms: 56 inches or more, or two fans. A 14 by 12 ft room (168 sq ft) takes a 44 to 50 inch fan.
What size ceiling fan for a 12x12 bedroom?
A 12 by 12 ft room is 144 sq ft, so a 36 to 42 inch fan. Standard sizes in that range are 36 and 42 inches.
How long a downrod do I need?
It depends on the ceiling height. An 8 ft ceiling takes a flush (hugger) mount; 9 ft takes 6 inches, 10 ft 12, 11 ft 18, 12 ft 24, 13 ft 36 and 14 ft 48 inches. Above that, add 12 inches for each extra foot. The goal is to hang the blades about 8 to 9 ft above the floor.
How high should a ceiling fan be?
The blades must be at least 7 ft above the floor for safety. Best is 8 to 9 ft. With a flush mount on an 8 ft ceiling the blades end up at about 7 ft, which is the lowest allowed.
Should I put two ceiling fans in a big room?
If the room is more than 1.5 times as long as it is wide and has more than 300 sq ft, use two fans, each sized for half the floor. A 400 sq ft room that is 25 by 16 ft takes two fans of 44 to 50 inches. One very large fan in a long room leaves the far ends still.
What does CFM per watt on a ceiling fan mean?
CFM is how much air the fan moves; the label (an ENERGY STAR or Department of Energy label) lists it for low, medium and high speed. CFM per watt divides that by the power it uses, so a higher number is more efficient. Many efficient DC-motor fans reach 100 CFM per watt or more at high speed. This is a goal to look for, not an ENERGY STAR requirement. See the list at energystar.gov/products/ceiling_fans.