Free illuminance / light level converter. Convert lux to foot-candles, foot-candles to lux, kilolux, phot, and lumens per square meter — for photography, indoor plants, workspace lighting, and grow lights. Instant results with a real-world brightness guide.
Lux • Foot-candles • lm/m² • phot
1 foot-candle = 10.7639 lux exactly (lumens per square foot vs per square meter). No rounding guesswork.
Built for camera light readings, workspace lighting standards, and indoor plant / grow-light targets.
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Illuminance is the amount of light falling on a surface, measured as luminous flux (lumens) per unit area. The SI unit is the lux (1 lux = 1 lumen per square meter). The US customary unit is the foot-candle (1 fc = 1 lumen per square foot). Because a square meter is larger than a square foot, the same light spread over a square meter is more diluted — so 1 foot-candle equals 10.7639 lux.
The core conversion: to convert foot-candles to lux, multiply by 10.764. To convert lux to foot-candles, divide by 10.764 (or multiply by 0.0929). Examples: an office lit to 500 lux is about 46 foot-candles; a 50 fc workshop is about 538 lux. Lighting designers in the US often specify foot-candles, while the rest of the world and most light meters use lux — making this conversion a daily need for photographers, architects, and facility managers.
Don't confuse illuminance with lumens. Lumens measure the total light output of a bulb (luminous flux), while lux and foot-candles measure how much of that light actually reaches a surface — which depends on distance and beam spread. A 800-lumen bulb produces very different lux at 1 meter versus 3 meters away. For plants, "lux" is a rough proxy; serious growers use PPFD (µmol/m²/s), but lux targets remain a useful everyday guide.
Direct sunlight: 32,000–100,000 lux. Overcast day: 1,000–10,000 lux. Sunrise/sunset: ~400 lux. Full moon: ~0.25 lux. Twilight: ~10 lux. Deep dusk: ~1 lux.
Office work: 300–500 lux. Detailed/drafting: 750–1,000 lux. Living room: 100–300 lux. Kitchen counter: 300–500 lux. Supermarket: 750–1,000 lux. Hospital exam: 1,000 lux.
Low-light houseplants: 1,000–2,500 lux. Medium: 2,500–10,000 lux. High-light/flowering: 10,000–50,000 lux. Seedlings: ~5,000–10,000 lux. Most plants want 12–16 hr/day.
1 fc = 10.764 lux. 1 lux = 0.0929 fc. 1 klx = 1,000 lux. 1 phot = 10,000 lux (lm/cm²). 1 nox = 0.001 lux. lm/m² = lux; lm/ft² = foot-candle.
Illuminance measures light falling on a surface, and it is routinely confused with three related quantities. Lumens measure total light output from a source; lux measures how much of it lands on a square metre; candela measures intensity in a direction; and nits measure light emitted from a display. Only illuminance answers "is this desk bright enough". The imperial unit, the foot-candle, is literally the illuminance from one candela at one foot, and one lux is one lumen per square metre. Because the same lumens spread over more area give less lux, illuminance falls with the square of distance from a point source.
lux = lumens ÷ area (m²)1 foot-candle = 10.7639 luxInverse square: E = I ÷ d²where:
Assumptions: Photopic (daylight-adapted) measurement, which weights wavelengths by human daytime sensitivity. It therefore does not describe how bright a light appears at night or to plants, which need PAR measurements instead.
Convert a US lighting requirement to metric and check it against normal practice.
Result50 foot-candles = 538 lux
For scale: full daylight is around 10,000–25,000 lux, an overcast day 1,000, and a well-lit street 10–20. Office lighting is far dimmer than outdoors, which is why sitting near a window feels dramatically brighter than any specification suggests.