Luminous flux in lumens (lm) to illuminance in lux (lx) calculator and how to calculate.

Enter the luminous flux in lumens, select area unit type, enter radius in meters for spherical light source or surface area

in square meters for any light source and press the *Calculate* button to get the illuminance in lux:

## Lumens to lux calculation formula

#### Calculation with area in square feet

The illuminance *E*_{v} in lux (lx) is equal to 10.76391 times the luminous flux *Φ*_{V}
in lumens (lm) divided by the surface area *A* in square feet (ft^{2}):

*E*_{v(lx)} = 10.76391 ×* Φ*_{V(lm)} / *A*_{(ft}2_{)}

The illuminance *E*_{v} in lux (lx) is equal to 10.76391 times the luminous flux *Φ*_{V}
in lumens (lm) divided by 4 times pi times the squared sphere radius r in feet (ft):

*E*_{v(lx)} = 10.76391 ×* Φ*_{V(lm)}* *
/* *(4⋅π⋅*r*_{(ft)}^{2})

#### Calculation with area in square meters

The illuminance *E*_{v} in lux (lx) is equal to the luminous flux *Φ*_{V}
in lumens (lm) divided by the surface area *A* in square meters (m^{2}):

*E*_{v(lx)} = *Φ*_{V(lm)}* *
/* A*_{(m}2_{)}

The illuminance *E*_{v} in lux (lx) is equal to the
luminous flux *Φ*_{V}
in lumens (lm) divided by 4 times pi times the squared sphere radius r in meters (m):

*E*_{v(lx)} = *Φ*_{V(lm)}* *
/* *(4⋅π⋅*r *^{2}_{(m}2_{)})

## Lux definition

The lux (symbol: lx) is the SI derived unit of illuminance, measuring luminous flux per unit area.[1][2] It is equal to one lumen per square metre. In photometry, this is used as a measure of the intensity, as perceived by the human eye, of light that hits or passes through a surface. It is analogous to the radiometric unit watt per square metre, but with the power at each wavelength weighted according to the luminosity function, a standardized model of human visual brightness perception. In English, "lux" is used as both the singular and plural form.[3]

The word is derived from the Latin word for "light", lux.

Illuminance is a measure of how much luminous flux is spread over a given area. One can think of luminous flux (measured in lumens) as a measure of the total "amount" of visible light present, and the illuminance as a measure of the intensity of illumination on a surface. A given amount of light will illuminate a surface more dimly if it is spread over a larger area, so illuminance is inversely proportional to area when the luminous flux is held constant.

One lux is equal to one lumen per square metre:

1 lx = 1 lm/m^{2} = 1 cd · sr / m^{2}.

A flux of 1000 lumens, spread uniformly over an area of 1 square metre, lights up that square metre with an illuminance of 1000 lux. However, the same 1000 lumens spread out over 10 square metres produces a dimmer illuminance of only 100 lux.

Achieving an illuminance of 500 lux might be possible in a home kitchen with a single fluorescent light fixture with an output of 12000 lumens. To light a factory floor with dozens of times the area of the kitchen would require dozens of such fixtures. Thus, lighting a larger area to the same level of lux requires a greater number of lumens.

As with other SI units, SI prefixes can be used, for example a kilolux (klx) is 1000 lux.

## Lumen definition

The lumen (symbol: lm) is the SI derived unit of luminous flux, a measure of the total quantity of visible light emitted by a source per unit of time. Luminous flux differs from power (radiant flux) in that radiant flux includes all electromagnetic waves emitted, while luminous flux is weighted according to a model (a "luminosity function") of the human eye's sensitivity to various wavelengths. Lumens are related to lux in that one lux is one lumen per square metre.

If a light source emits one candela of luminous intensity uniformly across a solid angle of one steradian, the total luminous flux emitted into that angle is one lumen (1 cd·1 sr = 1 lm). Alternatively, an isotropic one-candela light-source emits a total luminous flux of exactly 4π lumens. If the source were partly covered by an ideal absorbing hemisphere, that system would radiate half as much luminous flux—only 2π lumens. The luminous intensity would still be one candela in those directions that are not obscured.

The lumen can be thought of casually as a measure of the total amount of visible light in some defined beam or angle, or emitted from some source. The number of candelas or lumens from a source also depends on its spectrum, via the nominal response of the human eye as represented in the luminosity function.

The difference between the units lumen and lux is that the lux takes into account the area over which the luminous flux is spread. A flux of 1000 lumens, concentrated into an area of one square metre, lights up that square metre with an illuminance of 1000 lux. The same 1000 lumens, spread out over ten square metres, produces a dimmer illuminance of only 100 lux. Mathematically, 1 lx = 1 lm/m^{2}.

A source radiating a power of one watt of light in the color for which the eye is most efficient (a wavelength of 555 nm, in the green region of the optical spectrum) has luminous flux of 683 lumens. So a lumen represents at least 1/683 watts of visible light power, depending on the spectral distribution.

Electrical power equivalents for different lamps

(source: Wikipedia)

Minimum light output (lumens) | Electrical power consumption (watts) | |||
---|---|---|---|---|

Incandescent | Compact fluorescent | LED | ||

Non-halogen | Halogen | |||

200 | 25 | 3-5 | 3 | |

450 | 40 | 29 | 9–11 | 5–8 |

800 | 60 | 13–15 | 8–12 | |

1,100 | 75 | 53 | 18–20 | 10–16 |

1,600 | 100 | 72 | 24–28 | 14–17 |

2,400 | 150 | 30–52 | 24-30 | |

3,100 | 200 | 49–75 | 32 | |

4,000 | 300 | 75–100 | 40.5 |

Currently, we have around 5664 calculators, conversion tables and usefull online tools and software features for students, teaching and teachers, designers and simply for everyone.

You can find at this page financial calculators, mortgage calculators, calculators for loans, calculators for auto loan and lease calculators, interest calculators, payment calculators, retirement calculators, amortization calculators, investment calculators, inflation calculators, finance calculators, income tax calculators, compound interest calculators, salary calculator, interest rate calculator, sales tax calculator, fitness & health calculators, bmi calculator, calorie calculators, body fat calculator, bmr calculator, ideal weight calculator, pace calculator, pregnancy calculator, pregnancy conception calculator, due date calculator, math calculators, scientific calculator, fraction calculator, percentage calculators, random number generator, triangle calculator, standard deviation calculator, other calculators, age calculator, date calculator, time calculator, hours calculator, gpa calculator, grade calculator, concrete calculator, subnet calculator, password generator conversion calculator and many other tools and for text editing and formating, downloading videos from Facebok (we built one of the most famous Facebook video downloader online tools). We also provide you online downloanders for YouTube, Linkedin, Instagram, Twitter, Snapchat, TikTok and other social media sites (please note we does not host any videos on its servers. All videos that you download are downloaded from Facebook's, YouTube's, Linkedin's, Instagram's, Twitter's, Snapchat's, TikTok's CDNs. We also specialise on keyboard shortcuts, ALT codes for Mac, Windows and Linux and other usefull hints and tools (how to write emoji online etc.)

There are many very usefull online free tools and we would be happy if you share our page to others or send us any suggestions for other tools which will come on your mind. Also in case you find any of our tools that it does not work properly or need a better translation - please let us know. Our tools will make your life easier or simply help you to do your work or duties faster and in more effective way.

These below are the most commonly used by many users all over the world.

- Free online calculators and tools
- Time zones/Clocks/Dates calculators
- Free Online Units Conversion Calculators
- Free online web design tools
- Free online electricity & electronics tools
- Mathematics
- Online Tools
- Text Tools
- PDF Tools
- Code
- Ecology
- Others
- Free online downloaders for social media
- Marketing
- My PC / computer
- Free online electrical calculators and tools
- Free online financial calculators and tools
- Free online grade calculators and tools
- Free online lighting calculators and tools
- Free online math calculators and tools
- Free online wire calculators and tools
- Free online baby calculators and tools
- Free online body calculators and tools
- Electricity power consumptions/usage
- Candela to lumens free online calculation
- Candela to lumens free online calculator
- Candela to lux free online calculation
- Candela to lux free online calculator
- Footcandles to lux free online calculator
- Lumens to candela free online calculation
- Lumens to candela free online calculator
- Lumens to lux free online calculation
- Lumens to lux free online calculator
- Lumens to millicandela free online calculator
- Lumens to watts free online calculation
- Lumens to watts free online calculator
- Lux to candela free online calculation
- Lux to candela free online calculator
- Lux to footcandles free online calculator
- Lux to lumens free online calculation
- Lux to lumens free online calculator
- Lux to watts free online calculation
- Lux to watts free online calculator
- Millicandela to lumens free online calculator
- Watts to lumens free online calculation
- Watts to lumens free online calculator
- Watts to lux free online calculation
- Watts to lux free online calculator

And we are still developing more. Our goal is to become the one-stop, go-to site for people who need to make quick calculations or who need to find quick answer for basic conversions.

Additionally, we believe the internet should be a source of free information. Therefore, all of our tools and services are completely free, with no registration required. We coded and developed each calculator individually and put each one through strict, comprehensive testing. However, please inform us if you notice even the slightest error – your input is extremely valuable to us. While most calculators on Justfreetools.com are designed to be universally applicable for worldwide usage, some are for specific countries only.