Lux to Foot-candle Conversion Table
| Lux (lx) | Foot-candle (fc) | Reference Benchmark | Formula Step |
|---|---|---|---|
| 0.001 lx | 0.000093 fc | Overcast night sky with starlight only | 0.001 × 0.0929 = 0.000093 fc |
| 0.25 lx | 0.0232 fc | Full moon on a clear night at sea level | 0.25 × 0.0929 = 0.0232 fc |
| 1 lx | 0.0929 fc | Emergency pathway and exit corridor egress lighting | 1 × 0.0929 = 0.0929 fc |
| 10 lx | 0.929 fc | Residential hallway and twilight ambient outdoor light | 10 × 0.0929 = 0.929 fc |
| 50 lx | 4.645 fc | Residential living room or cinema auditorium ambient lighting | 50 × 0.0929 = 4.645 fc |
| 100 lx | 9.29 fc | Warehouse bulk storage aisles and commercial stairwells | 100 × 0.0929 = 9.29 fc |
| 200 lx | 18.581 fc | General dining room and school classroom background light | 200 × 0.0929 = 18.581 fc |
| 300 lx | 27.871 fc | Library reading room and hotel conference workspace | 300 × 0.0929 = 27.871 fc |
| 500 lx | 46.452 fc | Standard commercial open-plan computer office desktop | 500 × 0.0929 = 46.452 fc |
| 750 lx | 69.677 fc | Technical CAD drafting and mechanical inspection bench | 750 × 0.0929 = 69.677 fc |
| 1000 lx | 92.903 fc | Precision electronic manufacturing and watchmaking bench | 1,000 × 0.0929 = 92.903 fc |
| 2000 lx | 185.806 fc | Hospital operating surgical theater task illumination | 2,000 × 0.0929 = 185.806 fc |
| 5000 lx | 464.515 fc | Television broadcasting studio lighting stage | 5,000 × 0.0929 = 464.515 fc |
| 10000 lx | 929.03 fc | Overcast overcast midday outdoor daylight | 10,000 × 0.0929 = 929.03 fc |
| 25000 lx | 2322.576 fc | Full indirect daylight under clear blue sky | 25,000 × 0.0929 = 2,322.576 fc |
| 100000 lx | 9290.304 fc | Direct overhead tropical noon sunlight | 100,000 × 0.0929 = 9,290.304 fc |
Lux to Foot-candle Formula & Unit Definitions
The exact ratio derives from imperial-to-metric geometric surface definitions: 1 foot is defined as exactly 0.3048 meters, making 1 square foot equal to (0.3048 m)² = 0.09290304 square meters. Because luminous flux (lumens) is constant, dividing 1 lumen across 1 m² (lux) yields exactly 0.09290304 lumens per square foot (foot-candles). Conversely, concentrating 1 lumen into 1 ft² yields 1 / 0.09290304 ≈ 10.7639104 lx. Multiplying lux by 0.09290304 converts it directly to foot-candles.
Quick Estimation: To estimate lux to foot-candles mentally, divide the lux value by 10 (or multiply by 0.1 and subtract roughly 7%). For example, 500 lux in an office divided by 10 is approximately 50 fc (exact: 46.45 fc).
Lux (lx)
Source Unit- Coherent International System of Units (SI) derived unit of illuminance (lumen per square meter, lm/m²).
- Global standard for architectural, horticultural, and industrial lighting specifications outside the US.
- Intuitive scale where deep twilight is ~1 lx, a standard office is ~500 lx, and bright sunlight reaches ~100,000 lx.
Foot-Candle (fc)
Target Unit- Primary US customary and imperial illuminance unit (lumen per square foot, lm/ft²).
- Mandated standard in North American building codes, NFPA egress lighting, and IESNA design guidelines.
- Represents 10.764 times higher luminous density per unit area than lux, where 1 fc equals ~10.764 lx.
Frequently Asked Questions
Q.How do you convert lux to foot-candles accurately?
Multiply the illuminance in lux by approximately 0.092903 (or divide by 10.764). For example, 500 lx multiplied by 0.092903 yields 46.45 fc.
Q.What is the exact mathematical ratio between lux and foot-candles?
One foot-candle equals exactly 10.7639104 lux because 1 square meter contains 10.7639104 square feet. Conversely, 1 lux equals 0.09290304 foot-candles.
Q.What is the physical difference between Lux and Foot-candle?
Lux measures luminous flux per square meter (lm/m²) used internationally, while Foot-candle measures luminous flux per square foot (lm/ft²) used in North American building codes.
Q.How many foot-candles are needed for standard office desk work?
Standard commercial office workstations typically require 30 to 50 foot-candles (approximately 300 to 500 lux) for comfortable reading and computer display tasks.