Free Illumination Converter
Convert illumination units instantly — lux, foot-candle, phot, kilolux, millilux, lumen/m², W/m². Free, symmetrical, no sign-up.
Exact Conversion Formula & Multipliers
Illuminance is measured as luminous flux per unit area: 1 lux = 1 lumen per square meter by definition, while 1 foot-candle = 10.76391 lux (the ratio between a square meter and a square foot). Because foot-candles are defined per square foot rather than per square meter, the conversion factor isn't a clean round number — it's simply the area-conversion ratio applied to a light-measurement unit.
Practical Real-World Scenarios
- Architectural and interior lighting design: building codes and lighting specifications use lux internationally but foot-candles remain common in US commercial lighting standards.
- Photography and film production: light meters can display either unit, and cinematographers working across international crews need to convert on set.
- Agriculture and horticulture: grow-light intensity for indoor farming is specified in lux or the related PPFD units, with foot-candles appearing mainly in older US equipment manuals.
Historical & Technical Background
The lux was adopted as the SI-derived unit for illuminance in the mid-20th century, built from the lumen (a measure of total visible light output) divided by area. The foot-candle predates it, originally defined in the 19th century as the illuminance produced by one candle at one foot's distance — a delightfully literal, pre-electric definition that has persisted in US lighting standards long after standard candles stopped being the practical reference.
Precision & Accuracy Statement
Every conversion factor used on this page is checked against internationally recognized reference standards — BIPM SI Brochure photometric-unit definitions and NIST Special Publication 811 — rather than approximated or rounded for display. Where a constant is fixed by international definition (such as 1 inch = 2.54 cm, or standard gravity = 9.80665 m/s²), we use the exact defined value. Where a figure is a practical industry convention rather than a physical constant, that distinction is stated explicitly above so results are never presented with false precision.
How This Converter Works
Illumination (illuminance) measures the amount of light falling on a surface. Lux is the SI standard, foot-candles are used in the US film and photography industry. Our converter handles 10 illumination units.
Common Conversions
| Lux (lx) | Foot-candle (fc) | Context |
|---|---|---|
| 0.001 lx | 0.0001 fc | Moonless night sky |
| 1 lx | 0.093 fc | Full moonlit night |
| 400 lx | 37.2 fc | Office lighting standard |
| 1,000 lx | 92.9 fc | TV studio lighting |
| 10,000 lx | 929 fc | Overcast outdoor daylight |
| 100,000 lx | 9,290 fc | Direct sunlight |