Illuminance Converter
Convert between lux, foot-candle, phot, nox, lumen/m², lumen/cm², and lumen/ft² instantly.
Result
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All conversions
What is Illuminance Converter?
An illuminance converter lets you switch between units of illuminance — the amount of luminous flux (light) incident on a surface per unit area. The SI unit is the lux (lx), equal to one lumen per square metre. Foot-candles are used in US photography and architecture; phots appear in older CGS-based lighting literature.
How to use
- 1 Enter the illuminance value in the Value field.
- 2 Select the unit you are converting from in the From dropdown.
- 3 Select the unit you want to convert to in the To dropdown.
- 4 The result and a full table of all equivalent illuminances appear instantly.
- 5 Click the swap button to reverse the conversion.
Formula
Example calculation
Office lighting is typically 300–500 lux. To convert 400 lux to foot-candles: 400 × 0.092903 = 37.16 fc. Direct sunlight is about 100,000 lux = 9290 foot-candles.
Frequently asked questions
What is the difference between lux and lumens?
Lumens measure total luminous flux emitted by a source. Lux measures how much of that light lands on a surface: lux = lumens / area (m²). A 1000-lumen bulb creates 1000 lux on a 1 m² surface directly beneath it, or 100 lux spread over 10 m².
What is a foot-candle?
One foot-candle (fc) is the illuminance produced by one lumen per square foot. It is the imperial equivalent of lux. 1 fc = 10.7639 lux. Foot-candles are commonly used in US lighting design, photography, and film production.
What illuminance level is needed for office work?
The IESNA recommends 300–500 lux for general office tasks, and up to 750–1000 lux for detailed drafting or fine assembly work. Emergency and corridor lighting can be as low as 50–100 lux.
What is a nox?
The nox is an obsolete unit of illuminance equal to 0.001 lux, used historically for very low light levels such as moonlight and starlight. Moonlight produces about 0.1–1 lux (100–1000 nox); a clear starry sky without the moon is about 0.001 lux (1 nox).
What is the illuminance of direct sunlight?
Direct sunlight at noon in summer provides about 100,000 lux. An overcast sky provides 1,000–10,000 lux. Indoor daylight near a window is about 100–1000 lux depending on orientation and cloud cover.