Case 1
- Illuminance (fc)
- 50fc
538.20lx
Open with these valuesFoot-Candles to Lux Converter
538.20lx
Result: 538.20 lxMultiply the foot-candle reading by 10.7639. A 50 fc office is 538.20 lx; 100 fc is 1076.39 lx. The factor is exact, not measured: a foot-candle is one lumen per square foot, and a square foot has been exactly 0.09290304 m² since 1959.
The numbers at a glance
| Illuminance (fc) (fc) | Result (lx) |
|---|---|
| 0.00 | 0.00 |
| 20.00 | 215.28 |
| 40.00 | 430.56 |
| 50.00Your value | 538.20 |
| 60.00 | 645.83 |
| 80.00 | 861.11 |
| 100.00 | 1,076.39 |
Worked examples
Case 2
- Illuminance (fc)
- 30fc
322.92lx
Open with these valuesCase 3
- Illuminance (fc)
- 100fc
1,076.39lx
Open with these valuesHow it's calculated
lx = fc × 10.763910416709722
- StepTake the illuminance reading in foot-candles.
- StepMultiply by 10.7639, the number of lux in one foot-candle.
- ResultRead the result in lux, the unit European standards use.
Reference table
| Foot-candles | Where that occurs | Lux |
|---|---|---|
| 1 | One lumen on one square foot | 10.76 |
| 10 | A dimly lit room | 107.64 |
| 30 | The lower end of an office desk | 322.92 |
| 50 | A well-lit office desk | 538.20 |
| 100 | A bright retail floor | 1076.39 |
Questions
What is a foot-candle and how does it differ from lux?
A foot-candle is the imperial unit of illuminance — the luminous flux falling on one square foot. Lux measures the same thing per square metre instead. A square metre is larger, so one foot-candle is the bigger unit: 1 fc is about 10.76 lx.
How do I convert foot-candles to lux?
Multiply the foot-candle value by 10.763910416709722. The factor follows from the exact definition of the foot: 1 ft² is 0.09290304 m², so one foot-candle is 1 ÷ 0.09290304 lux. For example, 50 fc × 10.7639 is 538.20 lx.
What are typical illuminance levels?
A dim corridor is around 4–5 fc (50 lx), an office desk 30–50 fc (300–500 lx) and a supermarket floor 70 fc (750 lx). Outdoors, an overcast sky gives about 93 fc (1000 lx) and direct sunlight 9290 fc (100000 lx).
Why are foot-candles still used if lux is the SI unit?
US building codes, architectural specifications and older light meters were standardised on the imperial system, and North American film and photography studios kept the habit. European and international specifications expect lux, so the two keep meeting.
How do I convert back?
Divide the lux value by 10.763910416709722 — 538.20 lx is 50 fc. The relationship is linear, so doubling one doubles the other.
Sources and last check
Information, not professional advice.