Convert illuminance units — lux, foot-candle, phot, nox and more.
| Unit | Name | Value |
|---|---|---|
| fc | Foot-candle | 0.09290313 |
| ph | Phot | 0.0001 |
| nx | Nox | 1000 |
| klx | Kilolux | 0.001 |
| mlx | Millilux | 1000 |
Formula: Foot-candle = Lux × 0.0929
Multiply any Lux value by 0.0929 to get Foot-candle.
Reverse: Lux = Foot-candle × 10.76
Common illuminance levels — factor: 1 lx = 0.0929 fc
| Lux (lx) | Foot-candle (fc) | Context |
|---|---|---|
| 0.001 lx | 9.290e-05 fc | Moonless overcast night |
| 0.01 lx | 0.000929 fc | Dark countryside sky |
| 0.1 lx | 0.00929 fc | Moonlit night |
| 1 lx | 0.0929 fc | Full moon |
| 10 lx | 0.929 fc | Candle at 1 m |
| 50 lx | 4.645 fc | Living room typical |
| 100 lx | 9.29 fc | Corridor / stairway |
| 300 lx | 27.87 fc | Classroom |
| 500 lx | 46.45 fc | Office work / IES standard |
| 1000 lx | 92.9 fc | Studio lighting |
| 5000 lx | 464.5 fc | Bright overcast day |
| 1e+04 lx | 929 fc | SAD therapy lamp |
| 2.5e+04 lx | 2323 fc | Overcast daylight |
| 1e+05 lx | 9290 fc | Bright sunlight |
| 1.3e+05 lx | 1.208e+04 fc | Tropical noon sun |
lx × 0.0929 = fc. Round to ÷ 10.764.
500 lx = 46.5 fc (office). 10,764 lx = 1,000 fc.
fc × 10.764 = lx.
Specifies illuminance levels in lux (metric) or foot-candles (US) for architectural, retail, and workplace lighting per IES and EN 12464 standards.
Measures scene illuminance in lux with a light meter to set correct exposure for available-light photography.
Verifies that workplace lighting meets minimum requirements (typically 500 lx for offices, 300 lx for corridors) per local regulations.
Monitors grow-light illuminance in klx to optimize plant growth — fruiting plants typically need 20–60 klx.
Prescribes and measures light therapy intensity in lux for SAD treatment (10,000 lx standard) and circadian rhythm research.
Measures ambient light in lux to set appropriate display backlight levels for consistent image quality.
The lux (lx) is the SI unit of illuminance, defined as one lumen per square meter. It measures how much light falls on a surface, regardless of the surface's color or reflectivity. The lux was formally adopted by the International System of Units in 1960, superseding the older phot and metre-candle.
Lux levels define lighting requirements across all domains: emergency lighting minimum 1 lx, corridor lighting 100 lx, office work 500 lx, surgery 10,000–100,000 lx. Outdoor daylight ranges from 1,000 lx (overcast) to 130,000 lx (direct tropical sunlight).
Interesting fact: Human eyes can adapt to a remarkable range — from about 0.001 lx (moonless night) to over 130,000 lx (direct sunlight) — a factor of 100 million. Yet the lighting standards for reading (500 lx) are only 500 times brighter than a typical moonlit night (1 lx).
The foot-candle (fc) is the US customary unit of illuminance, defined as one lumen per square foot. One foot-candle = 10.7639 lux. It has been used in North American lighting specifications since the early 20th century and remains standard in US architectural and theatrical lighting.
US lighting standards use foot-candles: Illuminating Engineering Society (IES) specifies office work at 30–50 fc (300–500 lx), surgery at 200–400 fc, and roadway lighting at 0.5–2 fc. Stage lighting designers in North America universally work in foot-candles.
Interesting fact: The foot-candle's name reflects its origin — the illuminance on a surface one foot from a standard candle. The international candle standard was defined in 1909, and American lighting engineers adopted the foot-candle as their practical working unit from that era.
Illuminance measures light falling on a surface. The SI unit is lux (lm/m²); the US standard is foot-candles (lm/ft²). Key reference levels: moonless night ~0.001 lx, full moon ~1 lx, office work 500 lx, SAD therapy 10,000 lx, bright sunlight 100,000 lx.
Exact factor: 1 lx = 0.0929 fc. Reverse: 1 fc = 10.76 lx.
All conversions use IEEE 754 double-precision arithmetic, accurate to at least 8 significant figures.