Case 1
- Illuminance (lx)
- 500lx
46.45fc
Open with these valuesLux to Foot-Candles Converter
46.45fc
Result: 46.45 fcDivide the lux reading by 10.7639. An office at 500 lx is 46.45 fc; full sunlight at 100000 lx is 9290.30 fc. 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 (lx) (lx) | Result (fc) |
|---|---|
| 0.00 | 0.00 |
| 200.00 | 18.58 |
| 400.00 | 37.16 |
| 500.00Your value | 46.45 |
| 600.00 | 55.74 |
| 800.00 | 74.32 |
| 1,000.00 | 92.90 |
Worked examples
Case 2
- Illuminance (lx)
- 1000lx
92.90fc
Open with these valuesCase 3
- Illuminance (lx)
- 100000lx
9,290.30fc
Open with these valuesHow it's calculated
fc = lx ÷ 10.763910416709722
- StepTake the illuminance reading in lux from the meter.
- StepDivide by 10.7639, the number of lux in one foot-candle.
- ResultRead the result in foot-candles, the unit US lighting codes use.
Reference table
| Lux | Where that occurs | Foot-candles |
|---|---|---|
| 50 | A dim corridor | 4.65 |
| 500 | An office desk at standard level | 46.45 |
| 750 | A supermarket floor | 69.68 |
| 1000 | An overcast sky | 92.90 |
| 100000 | Direct sunlight | 9290.30 |
Questions
What is lux and how does it differ from foot-candles?
Lux is the SI unit of illuminance — the luminous flux falling on one square metre. Foot-candles measure the same thing per square foot 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 lux to foot-candles?
Divide the lux 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, 500 lx ÷ 10.7639 is 46.45 fc.
What are typical illuminance levels?
A dim corridor is around 50 lx (4.6 fc), an office desk 300–500 lx (28–46 fc) and a supermarket floor 750 lx (70 fc). Outdoors, an overcast sky gives about 1000 lx (93 fc) and direct sunlight 100000 lx (9290 fc).
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. Working with US clients or legacy equipment therefore still means converting.
How do I convert back?
Multiply foot-candles by 10.763910416709722 — 50 fc is 538.20 lx. The relationship is linear, so doubling one doubles the other.
Sources and last check
Information, not professional advice.