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To convert from Lux (lx) to Foot-candle (ft-cd), use the following formula:
Foot-candle (ft-cd)
= 110.76391× Lux (lx)
= 0.092903043596611268582× Lux (lx)
With 110.76391 is the ratio between the base units Foot-candle (ft-cd) and Lux (lx).
Let's convert 5 Lux (lx) to Foot-candle (ft-cd).
Using the formula:
5 × 0.092903043596611268582 = 0.46451521798305634291
Therefore, 5 Lux (lx) is equal to 0.46451521798305634291 Foot-candle (ft-cd).
How many lux are in one foot-candle? One Foot-candle (ft-cd) contains 10.76391 Lux (lx) — the inverse of the factor above. Multiplying by 0.092903043596611268582 takes you from lux to foot-candles; multiplying by 10.76391 brings you back.
Put in words: one lux equals 0.092903043596611268582 foot-candles, so the lux is the smaller unit of this pair. Converting between them never changes the amount of illuminance being measured — only the size of the unit you count it in.
Have you ever wondered how experts decide how bright the lights should be in an office or a movie studio?
The answer often comes down to a measurement called lux.
Lux (lx) is the standard unit used to measure illuminance—the total amount of visible light that hits a specific surface.
In simple terms, it measures how bright a light appears when it lands on something, like your desk or the floor.
Think of it like this: lumens measure the total amount of light coming from a source, while lux tells you how much of that light is actually landing on a specific area.
This measurement is crucial in many fields, from lighting design and photography to growing plants indoors.
The measurement of lux is directly connected to lumens, which measure the total light output from a source.
The formula is straightforward:
One lux is equal to one lumen distributed evenly over an area of one square meter.
This can be written as: 1 lx = 1 lm/m<sup>2</sup>.
This simple lux to lumen formula is essential for calculating and ensuring the correct lighting levels for any space or activity.
Measuring lux is vital for creating safe, efficient, and optimal lighting conditions across various industries.
To prevent eye strain and accidents, companies use lux measurements to ensure lighting levels meet workplace safety standards.
This helps create a comfortable and productive environment for employees in offices and factories.
In indoor farming and greenhouses, providing the right light is critical.
Since each plant has unique light intensity needs, measuring lux allows growers to fine-tune the environment, optimizing plant growth and maximizing crop yields.
In photography and filmmaking, lighting is everything.
Cinematographers and photographers use lux measurements to control exposure and create the desired mood in a scene. Consistent lux levels ensure every shot looks exactly as intended.
To get precise readings, professionals use a special tool called a lux meter.
This handheld device has a sensor that you can place on any surface to measure the illuminance in lux instantly.
A lux meter takes the guesswork out of determining if a space is adequately lit for its intended purpose.
A foot-candle (ft-cd) is the standard unit of illuminance, or light intensity, in the imperial system.
It's a fundamental concept used in lighting design to ensure spaces are adequately lit.
A foot-candle measures the amount of light that falls onto a specific surface.
To be precise, one foot-candle is the illuminance on a one-square-foot surface from a uniform light source of one candela that is exactly one foot away.
This direct relationship makes the foot-candle an intuitive unit for creating lighting plans in the imperial system.
It's important not to confuse foot-candles with lumens. While lumens measure the total light output from a source (like a lightbulb), foot-candles measure how much of that light actually reaches a surface.
The foot-candle is the imperial counterpart to the lux (lx), which is the standard unit for illuminance in the SI or metric system.
Since many lighting specifications are international, understanding how to convert between them is essential.
The conversion is straightforward:
For quick reference, here's a simple comparison table:
| Feature | Foot-candle (ft-cd) | Lux (lx) |
|---|---|---|
| System | Imperial | SI / Metric |
| Definition | 1 lumen / square foot | 1 lumen / square meter |
| Conversion | 1 ft-cd ≈ 10.764 lx | 1 lx ≈ 0.0929 ft-cd |
Using foot-candle measurements ensures that different environments are lit correctly for safety, comfort, and function.
Lighting standards often provide recommendations for various spaces. Here are a few common examples:
Lighting design is one of the last fields where two unit systems are used side by side in the same document, so the conversion is worth carrying in your head.
The awkward number is simply the number of square feet in a square metre. A foot-candle is one lumen per square foot; a lux is one lumen per square metre. Spread the same lumen over the larger metric area and you get a smaller number, which is why lux values always look about eleven times bigger than the same light expressed in foot-candles.
For rough fieldwork many designers divide or multiply by 10 and accept the 7% error, but that shortcut does not belong in a specification that has to be verified with a meter.
The foot-candle has been formally superseded by the lux almost everywhere, yet it remains the working unit of North American lighting practice for a practical reason: the standards are written in it.
Recommended illuminance levels published by the Illuminating Engineering Society (IES), along with a great deal of building code, energy code and utility rebate documentation, are expressed in foot-candles. So are the calibration scales on much of the installed base of light meters. An engineer who converts everything to lux still has to convert back to demonstrate compliance.
There is also a convenient coincidence that helped the unit stick. At a distance of one foot, a one-candela source produces exactly one foot-candle — the definition is directly readable from the name, which makes it easy to reason about point sources without a calculator.
Here are some quick reference conversions from Lux (lx) to Foot-candle (ft-cd):
| Lux | Foot-candles |
|---|---|
| 0.000001 lx | 9.2903043596611268582× 10-8 ft-cd |
| 0.001 lx | 0.000092903043596611268582 ft-cd |
| 0.1 lx | 0.0092903043596611268582 ft-cd |
| 1 lx | 0.092903043596611268582 ft-cd |
| 2 lx | 0.18580608719322253716 ft-cd |
| 3 lx | 0.27870913078983380575 ft-cd |
| 4 lx | 0.37161217438644507433 ft-cd |
| 5 lx | 0.46451521798305634291 ft-cd |
| 6 lx | 0.55741826157966761149 ft-cd |
| 7 lx | 0.65032130517627888007 ft-cd |
| 8 lx | 0.74322434877289014866 ft-cd |
| 9 lx | 0.83612739236950141724 ft-cd |
| 10 lx | 0.92903043596611268582 ft-cd |
| 20 lx | 1.8580608719322253716 ft-cd |
| 30 lx | 2.7870913078983380575 ft-cd |
| 40 lx | 3.7161217438644507433 ft-cd |
| 50 lx | 4.6451521798305634291 ft-cd |
| 100 lx | 9.2903043596611268582 ft-cd |
| 1000 lx | 92.903043596611268582 ft-cd |
| 10000 lx | 929.03043596611268582 ft-cd |
For all Illuminance converters, choose units using the From/To dropdowns above.