About this tool
The Ceiling Fan Size Calculator is a free, in-browser tool that recommends the correct ceiling-fan blade span (diameter) for a room from its floor area, and the downrod length to hang the fan at the right height for your ceiling. A fan that is too small barely moves air; one that is too large overwhelms a small room. Everything is computed locally in your browser and nothing you enter is uploaded.
The blade span follows the standard industry sizing chart by room area (length × width): up to 75 sq ft → 29–36 in, 75–144 sq ft → 36–42 in, 144–225 sq ft → 44–50 in, 225–400 sq ft → 50–54 in, and over 400 sq ft → 56–72 in (or two fans). The tool returns the recommended range plus a single best pick at the midpoint. For mounting, fan blades should sit about 8–9 ft above the floor (7 ft minimum), so an 8 ft ceiling uses a flush/hugger mount and taller ceilings add roughly 6 in of downrod per extra foot of height. Enter room dimensions and ceiling height in feet or meters.
As a worked example, a 14 ft × 12 ft room is 168 sq ft, which falls in the 144–225 sq ft band, so a 44–50 in fan is ideal — a 52 in-ish 47 in best pick. With a 9 ft ceiling the downrod is about 6 in; a 10 ft ceiling would use about 12 in. Also keep blade tips at least 18 in from walls and no lower than 7 ft above the floor for safe, effective airflow.