Illumination Converter

Illumination, more precisely called illuminance, measures how much light lands on a surface per unit area — how well-lit that surface actually is. It's the quantity a light meter measures directly, and it's the standard used in workplace lighting codes, photography exposure settings, and architectural lighting design to ensure a space is adequately (but not excessively) lit.

Our Illumination converter supports the SI unit, lux (lx), along with meter-candle and centimeter-candle, which are simply lux expressed with the historical "candle" terminology rather than "lumen." Foot-candle is the standard imperial unit, still widely used in the US lighting and photography industries. The phot is a CGS unit equal to exactly 10,000 lux, and the nox equals 0.001 lux, used for describing very low light levels such as moonlight or twilight conditions. The converter also includes flame (an older photometric unit), candela-steradian/square meter (dimensionally identical to lux), and lumen/square meter, centimeter, or foot — all equivalent framings of the same underlying quantity.

To use the converter, select your starting and target units from the dropdown lists and enter a value — the result is calculated instantly to up to 12 significant digits. For example, converting typical office lighting of 500 lux to foot-candles gives about 46.45 fc, a conversion needed constantly when comparing European lighting design standards (in lux) to US specifications (in foot-candles).

Illuminance standards guide lighting design across nearly every built environment: general office work is typically designed for 300-500 lux, detailed tasks like technical drafting or surgery may call for 1,000-10,000+ lux, while outdoor and security lighting is often much lower. Photographers and cinematographers use illuminance readings from handheld light meters to set exposure, and architects and lighting engineers use illuminance calculations to verify a design meets code-required minimums (or avoids uncomfortable, wasteful over-lighting). Because these standards and measurement tools are split between lux-based (most of the world) and foot-candle-based (US) conventions, accurate conversion is essential when working across regions or with imported lighting fixtures.

All conversion factors used in this tool are drawn from standard, internationally recognized photometric unit definitions, so results are dependable for lighting design, photography, and workplace safety compliance work. The converter is free, requires no account, and works equally well on desktop and mobile devices.

Illuminance is also the input to luminance calculations elsewhere in this section — a surface's apparent brightness depends on both the illuminance falling on it and its reflectance, so lighting designers routinely move between the two converters when verifying a space meets both light-level and brightness-appearance requirements.