Convert illuminance units — lux, foot-candle, phot, nox and more.
| Unit | Name | Value |
|---|---|---|
| lx | Lux | 1000 |
| fc | Foot-candle | 92.90313 |
| ph | Phot | 0.1 |
| nx | Nox | 1000000 |
| mlx | Millilux | 1000000 |
Formula: Foot-candle = Kilolux × 92.9
Multiply any Kilolux value by 92.9 to get Foot-candle.
Reverse: Kilolux = Foot-candle × 0.01076
Common illuminance levels — factor: 1 klx = 92.9 fc
| Kilolux (klx) | Foot-candle (fc) | Context |
|---|---|---|
| 1.000e-06 klx | 9.290e-05 fc | Dark night |
| 1.000e-05 klx | 0.000929 fc | Dark countryside |
| 0.0001 klx | 0.00929 fc | Moonlit night |
| 0.001 klx | 0.0929 fc | Full moon |
| 0.01 klx | 0.929 fc | Indoor bright |
| 0.1 klx | 9.29 fc | Overcast indoor |
| 0.5 klx | 46.45 fc | Office |
| 1 klx | 92.9 fc | Studio lighting |
| 5 klx | 464.5 fc | Bright overcast |
| 10 klx | 929 fc | SAD therapy lamp |
| 25 klx | 2323 fc | Overcast daylight |
| 50 klx | 4645 fc | Hazy sunlight |
| 100 klx | 9290 fc | Bright sunlight |
| 120 klx | 1.115e+04 fc | Typical sunlight |
| 130 klx | 1.208e+04 fc | Tropical noon |
klx × 92.9 = fc.
1 klx = 92.9 fc. 10 klx = 929 fc.
fc ÷ 92.9 = klx.
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.
Kilolux (klx) equals 1,000 lux and is used for high-illuminance environments including daylight simulation, horticulture, and phototherapy. Direct sunlight registers 80–130 klx; overcast daylight 1–25 klx.
Seasonal affective disorder (SAD) treatment lamps provide 10 klx at close range for 30-minute daily sessions. Horticulture lighting for fruiting plants targets 20–60 klx. Industrial quality control inspection stations may require 5–10 klx.
Interesting fact: The human circadian rhythm is most strongly reset by 10 klx blue-enriched light in the morning. Even 2.5 klx has measurable circadian effects — explaining why indoor living (typically 200–500 lx) can disrupt sleep cycles.
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 klx = 92.9 fc. Reverse: 1 fc = 0.01076 klx.
All conversions use IEEE 754 double-precision arithmetic, accurate to at least 8 significant figures.