Illuminance Converter

Lux (lx) is the SI unit of illuminance, measuring luminous flux per unit area in lumens per square meter (lm/m²). Foot-Candle (fc) is the imperial/US unit, measuring lumens per square foot. One foot-candle equals approximately 10.76391 lux. Lux is widely used internationally (Europe, Asia, etc.), while foot-candle remains common in the United States for lighting design and building codes. The conversion factor comes from the ratio of square meters to square feet: 1 m² ≈ 10.76391 ft².

To convert lux to foot-candle, multiply the lux value by 0.092903. The formula is: fc = lx × 0.092903. For example, 500 lux × 0.092903 = 46.45 foot-candles. This tool performs the conversion instantly — simply enter your lux value, select "Lux" as the input unit and "Foot-Candle" as the output unit, and the result appears immediately.

Typical recommended illuminance levels vary by activity:
• Living rooms & bedrooms: 50–300 lux (5–28 fc)
• Kitchens & bathrooms: 200–500 lux (19–46 fc)
• Office desks (general): 300–500 lux (28–46 fc)
• Detailed office work: 500–750 lux (46–70 fc)
• Retail displays: 750–1500 lux (70–139 fc)
• Precision assembly: 1000–2000 lux (93–186 fc)
These standards are based on IES (Illuminating Engineering Society) and CIE recommendations.

A Phot (ph) is a CGS (centimeter-gram-second) unit of illuminance equal to 10,000 lux or 1 lumen per square centimeter. It's an older unit rarely used today but occasionally appears in legacy scientific literature and some European contexts. 1 phot = 10,000 lx = 929.03 fc. The unit was more common before the widespread adoption of SI units in lighting science.

The United States continues to use foot-candle primarily due to historical precedent and building code continuity. US construction and electrical codes (like NFPA, NEC, and local building regulations) traditionally specify lighting requirements in foot-candles. Switching entirely to lux would require updating thousands of codes, standards, and industry practices. However, many modern US lighting professionals use both units interchangeably, and LED fixture specifications often list both lx and fc values.

Yes! This illuminance conversion tool is completely free with no registration required. You can perform unlimited conversions between lux, foot-candle, phot, and nox instantly. There are no hidden fees, no ads that interfere with functionality, and no usage limits. We built this tool to help lighting designers, engineers, architects, photographers, and anyone working with light measurements.

Nox (nx) is a unit of illuminance equal to 0.001 lux (1 millilux). It's used for measuring extremely low light levels, such as in night vision applications, astronomical observations, and dark-sky studies. 1 nox = 0.001 lx = 0.0000929 fc. While not commonly used in everyday lighting design, nox is valuable in specialized fields where quantifying near-darkness conditions is important, such as wildlife behavior research and low-light sensor calibration.