unit of energy measurement

Definition of Foot-Candle

Foot-candle (fc) is a unit of measurement that describes the amount of light reaching a certain point in a specific area. It is the amount of light that falls on a one-square-foot area located one foot away from a light source.

Lumen is the foundational unit, measuring the quantity of light produced by a light fixture.

schematic diagram of a foot-candle measurement

Foot-candle measurements can be affected by:

  • Distance between the lit surface and the light source
  • Angle of the light beam
  • Height of the light source
  • Reflectance of the surface
  • Presence of any obstructions or shadows.

Foot-candles are an important measurement to consider when determining the amount of light needed to illuminate a particular space safely and efficiently.

Here is a comparison between various lux and foot-candle thresholds and the types of spaces they suit.

Light Level (Foot Candles) Light Level (Lux) Suitable Type Of Space
10–30 fc 100–300 lux
  • Loading dock
  • Lounge
  • Restroom
5–10 fc 50–100 lux
  • Parking basement
  • Stairway
  • Storage room
20–30 fc 200–300 lux
  • Dining area
  • Living quarters
  • Gym
  • Office
30–50 fc 300–500 lux
  • Art exhibit
  • Kitchen
  • Reading area
  • Electrical room
  • Workshop
75–120 fc 750–1200 lux Laboratory

Example of Foot-Candle in a Sentence

"The navigation lights on my boat need to produce at least 2.5 foot-candles of light to meet the safety requirements set by the Coast Guard."

Synonyms: lumen per square foot, lux

Related Terms for Foot-Candle