Illuminance Calculator: Lux from Lumens and Area or from Candela and Distance, with Foot-Candles
Lux from lumens or candela, and lux to foot-candles.
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How this calculator works
Choose lumens on an area, candela at a distance, or a lux value to convert.
Enter the values.
The calculator gives the illuminance in lux and foot-candles.
Formulas used
- E = \frac{\Phi}{A}
- E = \frac{I\cos\theta}{d^2}
- 1\ \text{fc} = 10.7639\ \text{lx}
Worked example
With the default numbers in the calculator above:
- Illuminance: 250 lux
- Illuminance in foot-candles: 23.226 foot-candles
Change the numbers in the calculator to see the full working, every step, for your own case.
A second worked example
A different case, with these numbers: What do you know? The candela of a source, its distance and the angle.
- Illuminance: 200 lux
- Illuminance in foot-candles: 18.581 foot-candles
Common questions
What is a lux?
One lumen of light falling on one square metre.
What is a foot-candle?
One lumen per square foot, which is 10.76 lux.
How much light does an office need?
About 320 lux for general office work and 500 lux for drawing and fine detail, according to lighting standards.
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Further reading: Any lighting design text, and the lighting standard that applies to your workplace.
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