Ceiling Fan Size Calculator
Pick the right ceiling fan blade span for a room based on its floor area.
Last updated · View algorithm, constants and default inputs (JSON)
About this calculator
Blade span and fan count are room-area heuristics: the model assigns one fan up to 400 square feet and rounds additional fans up beyond that. Mounting distance is measured down from the ceiling. Check the fan maker’s clearance and installation instructions for your room.
Worked example
calculated with the default values below
Room length 14 ft · Room width 12 ft · Ceiling height 9 ft Recommended blade span 52 in · Fans needed 1 · Room area 168.0 sq ft · Blade height below the ceiling 12.00 in · Mounting Flush mount is fine at this ceiling height
General background references
Disclaimer
These calculators provide planning estimates only. Building codes, wiring regulations and safety requirements differ by country and change over time, and nothing here replaces a licensed professional or a permit. For structural, electrical or gas work, follow local code and have the installation inspected.
Implementation source
This record describes the implementation used by this page. It is not independent validation. External references, when available, support only the stated formula or definition; estimates and custom rules retain their own assumptions.
Formula and variables
span: 36 (A≤75), 42 (≤144), 52 (≤225), 60 (≤400), 72 (>400) in; fans = ⌈A ÷ 400⌉
- A
- Floor area (sq ft)
- span
- Blade span (in)
- fans
- Number of fans
Blades should hang 8–9 ft above the floor; add 12 in of downrod per foot above a 9 ft ceiling.
Frequently asked questions
Why does a room over four hundred square feet need two ceiling fans?
The tool caps a single fan at a 72-inch span because one blade set only circulates air across about 400 square feet, so any room larger returns fanCount = ceiling(area ÷ 400) and recommends two or more. A 14 by 12 foot room is 168 sq ft and gets a 52-inch fan, while a 500 sq ft space needs two. Mount height also rises with the ceiling: blades sit 12 inches down at 9 feet and gain a foot for every foot higher.