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Converters

Illuminance Converter

Convert illuminance accurately between lux, millilux, kilolux, megalux, foot-candles, and phot using fixed unit definitions.

Example: an illuminance of 500 lux. How many foot-candles is that?
Result 46.45152 fc 500 lx = 46.45152 fc
One-unit equivalent 1 lx = 0.092903 fc A quick way to understand the relationship between the two units.

✓ Conversion factors match data and definitions from the National Institute of Standards and Technology (NIST)

How is the conversion calculated? The value is converted to lux first, the SI unit of illuminance, then to the requested unit using fixed factors. The foot-candle factor is derived from the exact international foot.

This calculation runs in your browser. Your values are not sent to our server.

How it works

  1. Enter an illuminance value, then choose the current and target units.
  2. Example: 500 lux equals exactly 46.45152 foot-candles when derived from the exact international foot.
  3. The converter uses lux, the SI unit of illuminance, as its internal reference.
  4. NIST lists 1 phot = 10,000 lux and approximately 1 foot-candle = 10.76391 lux.
  5. For foot-candles, the engine derives the factor from the exact international foot: 1 ft = 0.3048 m, rather than storing a shortened decimal.
  6. This tool converts illuminance only. It does not convert luminance units such as cd/m² or footlamberts, which measure a different quantity.

FAQ

How many lux are in 1 foot-candle?

1 foot-candle equals about 10.7639104167 lux. The converter derives this from the exact international foot.

How many foot-candles are in 1 lux?

1 lux equals exactly 0.09290304 foot-candle when the international foot definition is used.

How many lux are in 1 phot?

1 phot equals exactly 10,000 lux.

Is lux the same as luminance?

No. Lux measures illuminance falling on a surface, while luminance describes light emitted or reflected in a direction and uses units such as cd/m².

Can illuminance be negative?

No. A physical illuminance magnitude cannot be negative, so negative inputs are rejected.

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