foot-candle (fc)
1 foot-candle = 10.76391042 lux
What is foot-candle?
A foot-candle is an imperial illuminance unit equal to one lumen per square foot. It is used in the United States for stage and event lighting specifications, photographic exposure references, and building lighting compliance standards.
Notes: Imperial illuminance unit
Real-world uses
Foot-candles are used in US lighting design, building codes, and OSHA workplace safety standards. The Illuminating Engineering Society (IES) recommends 30–50 fc for office work, 5–10 fc for corridors, and 75–100 fc for detailed tasks. US photography light meters often display in fc.
History
The foot-candle was defined as the illumination on a surface one foot away from a standard candle. It has been used in American lighting engineering since the 19th century. While most countries use lux, the foot-candle remains the standard in US building codes and IES guidelines.
Common mistakes
Assuming 1 foot-candle equals 1 lux. Actually, 1 fc ≈ 10.764 lux, so a 50 fc requirement equals about 538 lux. Also, foot-candles should not be confused with candlepower or candela, which measure luminous intensity, not illuminance.
When is this conversion used?
Converting between foot-candle and lux is common when working across metric and imperial systems, such as international trade, travel between countries with different measurement standards, or following instructions from a different region.
How to convert foot-candle to lux
To convert foot-candle to lux, multiply the value by 10.76391042.
Conversion formula (from base unit)
x * 10.7639104167
Measurement standards
The lux is the SI derived unit of illuminance, defined as one lumen per square metre (lm/m²). The CIE (International Commission on Illumination) provides standard illuminance recommendations for various visual tasks, which most national standards bodies adopt directly.
Did you know?
Direct sunlight at noon on a clear day delivers roughly 100,000 lux, while a dimly lit room might have only 50 lux. The human eye can function across a range of over 10 billion to one from starlight to direct sun — one of the widest dynamic ranges of any biological sensor.
| foot-candles | lux |
|---|---|
| 0.1 | 1.07639104 |
| 0.5 | 5.38195521 |
| 1 | 10.76391042 |
| 2 | 21.52782083 |
| 5 | 53.81955208 |
| 10 | 107.63910417 |
| 25 | 269.09776042 |
| 50 | 538.19552084 |
| 100 | 1,076.39104167 |
| 250 | 2,690.97760418 |
| 500 | 5,381.95520835 |
| 1,000 | 10,763.9104167 |
Common values
| foot-candles | lux | |
|---|---|---|
| Full moon, clear night | 0.0092903 foot-candles | 0.1 lux |
| Living room lighting | 9.290304 foot-candles | 100 lux |
| Office lighting | 46.45152 foot-candles | 500 lux |
| Overcast daylight | 92.90304 foot-candles | 1,000 lux |
| Direct sunlight | 9,290.30400001 foot-candles | 100,000 lux |
Full foot-candle conversion table
| Unit | Value | Factor |
|---|---|---|
| lux | 1 fc = 10.76391042 lx | × 10.76391042 |
| lumen per square metre | 1 fc = 10.76391042 lm/m² | × 10.76391042 |
| phot | 1 fc = 0.00107639 ph | × 0.00107639 |