Illuminance Converter
Convert between lux, foot-candle, and phot illuminance units.
About this tool
Illuminance is the amount of light falling on a surface, measured in units that vary by region and industry. This converter helps you translate between lux (the metric standard used worldwide), foot-candles (common in North American photography and film), and phots (a unit occasionally seen in scientific contexts). Whether you're adjusting lighting for photography, designing an architectural space, or working with lighting specifications from different sources, having a quick way to convert between these units prevents costly mistakes and ensures compatibility across projects.
Simply select your source unit from the dropdown, enter the illuminance value, and the converter instantly displays the equivalent in all three units. The tool works entirely in your browser—no data is sent anywhere, and results appear immediately. You can switch units as many times as needed, making it ideal for quick reference during design sessions, equipment configuration, or when comparing specifications from international suppliers.
Lighting designers, photographers, cinematographers, and architects benefit most from this tool, as they often receive specifications in different units depending on equipment origin and regional standards. Keep in mind that these are unit conversions only—they assume you already know the illuminance value on your surface and simply need to translate it. For actual light measurement on set or in a space, you'd use a lux meter or light meter, then bring those readings here to compare against design targets.
Frequently Asked Questions
Code Implementation
# Illuminance unit conversion in Python
# Conversion factors relative to lux (lx)
ILLUM_TO_LUX = {
"lux": 1.0,
"foot_candle": 10.7639, # 1 fc = 10.7639 lux
"phot": 10000.0, # CGS unit: 1 ph = 10000 lux
"nox": 0.001, # 1 nox = 0.001 lux
}
def convert_illuminance(value: float, from_unit: str, to_unit: str) -> float:
lux = value * ILLUM_TO_LUX[from_unit]
return lux / ILLUM_TO_LUX[to_unit]
# Core formula: fc ↔ lux
def lux_to_fc(lux: float) -> float:
return lux / 10.7639
def fc_to_lux(fc: float) -> float:
return fc * 10.7639
# Examples
print(lux_to_fc(500)) # 46.45 (office 500 lux → fc)
print(fc_to_lux(50)) # 538.2 (stage lighting)
print(convert_illuminance(1000, "lux", "foot_candle")) # 92.9
print(convert_illuminance(100, "foot_candle", "lux")) # 1076.39Comments & Feedback
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