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Convert illuminance from imperial to metric units instantly
1 foot-candle = 10.764 lux
lux = foot-candles × 10.764
| Foot-Candles (fc) | Lux (lx) | Typical Application |
|---|---|---|
| 5 fc | 53.8 lx | Corridors, public areas |
| 10 fc | 107.6 lx | Stairways, lobbies |
| 20 fc | 215.3 lx | General office lighting |
| 30 fc | 322.9 lx | Libraries, classrooms |
| 50 fc | 538.2 lx | Detailed office work |
| 75 fc | 807.3 lx | Drafting, design work |
| 100 fc | 1,076.4 lx | Detailed inspection |
| 200 fc | 2,152.8 lx | Surgical procedures |
| 500 fc | 5,382.0 lx | TV/film production |
| 1,000 fc | 10,764.0 lx | Bright daylight indoors |
| 5,000 fc | 53,820.0 lx | Direct sunlight |
| 10,000 fc | 107,640.0 lx | Full summer sun |
Foot-candles and lux both measure illuminance - the intensity of light falling on a surface per unit area. One foot-candle represents the illumination of one lumen uniformly distributed over one square foot, while one lux represents one lumen per square meter. The conversion factor (10.764) comes from the area ratio between square meters and square feet. Foot-candles remain the standard in US lighting codes and OSHA regulations, while lux is used internationally and in scientific contexts. Professional lighting designers must be fluent in both systems when working on international projects or consulting various standards. Understanding these units is crucial for workplace safety, architectural design, photography, film production, and any application requiring precise illumination control. Both measurements require calibrated light meters for accurate readings.
Historical precedent and established regulations keep foot-candles in use. US building codes, OSHA standards, and ANSI/IES recommendations specify foot-candles because converting decades of documentation would be costly and potentially confusing. However, many modern US lighting professionals work in both systems, and newer standards increasingly include lux equivalents. Most professional light meters display both units simultaneously.
No practical difference exists - they measure the same physical quantity using different area units. The choice is purely conventional based on location and industry standards. A properly lit office requiring 50 foot-candles needs 538 lux - these represent identical illumination. The only consideration is precision: lux values are numerically larger, so they may appear more precise when rounded to whole numbers (538 lux vs. 50 fc).
Standard office lighting ranges from 30-50 foot-candles (323-538 lux) for general work areas. Computer work requires 20-50 fc, while detailed tasks like drafting need 50-100 fc (538-1,076 lux). Conference rooms typically use 30 fc, and corridors 5-10 fc. These are maintained illuminance levels, meaning the lighting design provides higher initial levels to account for lamp degradation and dirt accumulation over time.
Use a calibrated light meter (also called illuminance meter or lux meter) set to foot-candles mode. Position the meter's sensor at the work surface height, oriented upward to capture incident light. Take multiple readings across the space and average them, as illuminance varies significantly with location. Ensure lights have been on for 15-30 minutes to reach stable output, and account for daylight if present. Professional meters cost $100-$500, with ±2-5% accuracy.
LEDs with the same lumen output produce identical foot-candle measurements as other technologies - the bulb type doesn't affect illuminance readings. However, LEDs often have different beam patterns (directional vs. omnidirectional) affecting light distribution. A 60W-equivalent LED and 60W incandescent both producing 800 lumens will create the same foot-candles at a given location, though the spatial distribution pattern may differ based on bulb design.
Not directly - they measure different properties. Foot-candles measure illuminance (light density at a surface), while lumens measure total light output from a source. The relationship depends on geometry: distance from source, beam angle, and surface area. For example, 1,000 lumens from a point source creates 79.6 fc at one foot distance, but only 19.9 fc at two feet. Lighting design software uses photometric calculations to predict illuminance from lumen output.