Convert illuminance units — lux, foot-candle, phot, nox and more.
| Unit | Name | Value |
|---|---|---|
| lx | Lux | 10.7639 |
| ph | Phot | 0.00107639 |
| nx | Nox | 10763.9 |
| klx | Kilolux | 0.0107639 |
| mlx | Millilux | 10763.9 |
Formula: Kilolux = Foot-candle × 0.01076
Multiply any Foot-candle value by 0.01076 to get Kilolux.
Reverse: Foot-candle = Kilolux × 92.9
Common illuminance levels — factor: 1 fc = 0.01076 klx
| Foot-candle (fc) | Kilolux (klx) | Context |
|---|---|---|
| 0.0001 fc | 1.076e-06 klx | Moonless night |
| 0.001 fc | 1.076e-05 klx | Dark countryside |
| 0.01 fc | 0.0001076 klx | Moonlit road |
| 0.1 fc | 0.001076 klx | Full moon |
| 1 fc | 0.01076 klx | Dark corridor |
| 5 fc | 0.05382 klx | Stairway / passage |
| 10 fc | 0.1076 klx | Lobby |
| 30 fc | 0.3229 klx | Office minimum |
| 50 fc | 0.5382 klx | IES office standard |
| 100 fc | 1.076 klx | Surgical minimum |
| 200 fc | 2.153 klx | Detailed surgery |
| 500 fc | 5.382 klx | Close inspection |
| 1000 fc | 10.76 klx | Extreme inspection |
| 5000 fc | 53.82 klx | Hazy sunlight |
| 1.2e+04 fc | 129.2 klx | Bright sun |
fc ÷ 92.9 = klx.
92.9 fc = 1 klx. 929 fc = 10 klx (SAD therapy).
klx × 92.9 = fc.
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 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.
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.
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 fc = 0.01076 klx. Reverse: 1 klx = 92.9 fc.
All conversions use IEEE 754 double-precision arithmetic, accurate to at least 8 significant figures.