Luminance Unit Converter
Illuminance and luminance describe different aspects of light. Illuminance (lux or foot-candles) is the amount of luminous flux (light) per unit area arriving at a surface. This converter handles illuminance units including lux (lm/m2), foot-candles (lm/ft2), millilux, kilolux, and the CGS unit phot. The exact factor between lux and foot-candles comes from the exact definition of the foot: 1 foot = 0.3048 m exactly, so 1 ft2 = 0.09290304 m2 exactly, and 1 fc = 1/0.09290304 lux = 10.7639 lux.
Illuminance conversion factors (referenced to lux)
1 lux = 1,000 mlux = 0.001 klux = 0.09290304 foot-candles = 0.0001 phot
The foot-candle factor uses the exact definition: 1 ft = 0.3048 m, so 1 ft2 = 0.09290304 m2. One phot = 10,000 lux (1 lm/cm2).
Typical illuminance levels
- 0.001 lux: Moonless overcast night sky.
- 1 lux: Candlelight at 1 meter distance.
- 300 to 500 lux: IES recommended office work illuminance.
- 1,000 lux: Television studio, overcast day outdoors.
- 10,000 lux: Full daylight (not direct sun).
- 100,000 lux: Direct sunlight at noon.
Luminance converter: frequently asked questions
What is the difference between lux, lumens, and candelas?
Lumens (lm) measure total luminous flux emitted by a source. Lux (lx) measures illuminance: lumens per square meter at a surface. Candelas (cd) measure luminous intensity in a direction. For example, a 100 lm flashlight creates more lux on a nearby wall than on a distant one.
How do I convert lux to foot-candles?
Divide lux by 10.7639 to get foot-candles. One foot-candle is the illuminance produced by one lumen over one square foot. Since 1 m2 = 10.7639 ft2, one lux = 0.09290304 foot-candles.
What illuminance is recommended for office work?
The Illuminating Engineering Society (IES) recommends 300 to 500 lux (28 to 46 foot-candles) for general office work and 500 to 1,000 lux for detailed tasks. Outdoor sunlight on a clear day is typically 100,000 lux or more.
What is luminance and how does it differ from illuminance?
Illuminance (lux) is the light falling on a surface. Luminance (candela per square meter, cd/m2) is the light reflected or emitted from a surface toward the observer. A monitor screen has a typical luminance of 200 to 400 cd/m2. This converter focuses on illuminance units.
What is a phot?
A phot (ph) is the CGS unit of illuminance equal to 10,000 lux (1 lumen per cm2). It is rarely used in modern work but appears in older lighting engineering literature. One foot-candle equals approximately 0.929 phot.
Official sources
- NIST Special Publication 811: Guide for the Use of the International System of Units (SI).
- BIPM SI Brochure: The International System of Units.
Reviewed by the CalculatorHub team, edited by James Graham, 15 June 2026. See our methodology.