Ceiling Fan Size Calculator

Recommends a blade span for your room size, an estimated downrod length for your ceiling height, ENERGY STAR airflow and efficiency targets, and the yearly running cost of the fan.

For anyone choosing a ceiling fan.

Last updatedHow we build & check our tools
Results will appear here once you enter your values.

How the recommendation works

Area is length x width. If it is over 400 sq ft, the tool splits it across two fans. Blade span comes from the area band, with shared boundaries going to the smaller band. For airflow and efficiency targets it uses a representative diameter in each band: 36, 42, 44 and 52 inches.

With the defaults (14 x 12 ft, 9 ft ceiling, 30 W, 8 hours per day, $0.16 per kWh) the result is a 44 inch fan, a flush mount, a high-speed target of about 2,640 CFM, an efficiency target of about 88.9 CFM per watt, and an annual cost of $14.02.

  • Room: up to 800 sq ft total, ceilings 8 to 30 ft.
  • Power: 0 to 1,000 W per fan, 0 to 24 hours per day.
  • Rate: $0 to $10 per kWh.

Limits of the estimate

Blade span is a general guide. Room shape, furniture, how you use the space and the fan's actual airflow all change comfort. Do not hang a fan from a ceiling box that is not rated for fan support, and follow the manufacturer's instructions for mounting height and clearance.

  • Electrical work: have a licensed electrician install a fan-rated box and wiring if unsure.
  • Clearance: blades should be at least 7 ft above the floor.
  • Placement: sloped ceilings need an angle-rated mount.

Sources and next steps

ENERGY STAR, Ceiling Fan Basics (room-size table credited to the American Lighting Association, 2003; blades 8 to 9 ft above the floor and at least 7 ft). ENERGY STAR, Ceiling Fans Key Product Criteria, standard fans. Energy arithmetic: kWh = W x hours x days / 1,000.

To see how much a fan can offset your cooling bill, use the SEER savings calculator and AC BTU calculator. The kWh cost calculator prices any other appliance, and the CFM calculator sizes a ventilation fan.

Frequently Asked Questions

Common questions about the Ceiling Fan Size Calculator

Based on room area from the ENERGY STAR ceiling fan guidance: up to 75 sq ft takes 29 to 36 inches, 76 to 144 sq ft takes 36 to 42, 145 to 225 sq ft takes 44, and 226 to 400 sq ft takes 50 to 54. Over 400 sq ft the tool recommends two fans, each sized for half the area. A 14 x 12 ft room is 168 sq ft, so the answer is 44 inches.

Sources & References

International System of Units (SI): energy, work and heat

Energy, work and heat is measured in the joule (J); 1 cal = 4.184 J. Conversions between SI and other units use exact, internationally agreed factors maintained by NIST.
→Source: NIST — International System of Units (SI)

International System of Units (SI)

Authoritative definitions for energy, work and heat, from the BIPM SI Brochure (9th edition), the defining reference for the SI.
→Source: BIPM — SI Brochure (9th ed.)

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