Illuminance Converter
Convert between illuminance units instantly: lux, foot-candle, phot, nox, and kilolux. Free, accurate, and 100% in your browser.
Reference
How does illuminance conversion work?
Illuminance conversion uses fixed ratios with the lux (lx) as the base unit. 1 foot-candle = 10.7639 lux, 1 phot = 10,000 lux, 1 nox = 0.001 lux, and 1 kilolux = 1,000 lux. Illuminance measures the amount of luminous flux per unit area — how much visible light falls on a surface. The lux is the SI unit, defined as one lumen per square meter. Different units are used in different industries and regions.
Unit reference
Nox (nx) — one millilux (0.001 lx). Used for very low light levels like starlight and moonlight measurements. Lux (lx) — the SI unit of illuminance. 1 lux = 1 lumen per square meter. Common reference: full daylight is ~10,000–25,000 lx, office lighting is ~300–500 lx. Foot-candle (fc) — one lumen per square foot ≈ 10.764 lux. Widely used in the US for architectural and photography lighting. Kilolux (klx) — one thousand lux. Used for bright environments like direct sunlight. Phot (ph) — a CGS unit equal to 10,000 lux. Rarely used today but found in older scientific literature.
Common use cases
Architecture — convert between lux and foot-candles for lighting design specifications. Photography — determine proper exposure based on ambient light measurements. Workplace safety — verify that lighting meets regulatory standards (often specified in lux or foot-candles). Horticulture — measure and convert light levels for plant growth requirements. Display calibration — convert screen brightness measurements between units.
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