Calculate lux level

The lux level can be determined from other measurements, but it will depend on what information you have. (Like the weight of a bucket of water can be determined from the volume of water in the bucket -- but you need to be able to measure that volume of water.)

Thankx for reply, i know area of room and wattage of fixture thats it, as per formula we should know luminus of lux, so is there any alternate method to find out lux level with out luminus of lamp?

Measure it with a lux meter.

Still project is not yet been started, i have to design lighting layout.i can fix approx fixtures but it wil achieve approppriete lux?

What does the literature from the selected manufacturer say?

Here is some more info, but it probably won't help you much because there is one key unknown quantity: the reflectivity of the walls.

First I'll give you some very rough values for different kinds of lighting, all extrapolated to 100 Watts to make the comparison easy. I use the data for a 60W incandescent lamp and extrapolate that to a 100 watts (as if you were using 1.667 60-watt lamps); then the data for a 25W CFL (as if you were using 4 of them); and for a 60W LED lamp (here again as if you were using 1.667 of them).

100W IC lamp = 1400 Lumens; 100W CFL = 4000 Lumens; 100W LED = 6500 Lumens. (But remember these are very rough estimates, and values can vary a lot.)

You can then, as a first order estimate, calculate the Lux at the wall surface from the total number of lumens divided by the area of the walls, floor and ceiling in meters -- as if all of the light came from a single bulb at the center of a sphere having a surface area equal to the area of your room, and all of the walls were black.

BUT, there is a multiplier effect due to the reflectivity of the walls and some shadowing effects of the luminaire itself and where it is located. Let's say your luminaire was well-located with neglectable shadowing and the walls were black. You'd get a Lux value as above, where you divide the room surface area by the total lumens. Now suppose the room walls were gray with a reflectivity of 50%. You might have a multiplier effect (photons striking multiple walls before getting absorbed) of 5, so your net Lux compared to a black-walled room might be (1+50%)⁵ = (1.5)⁵ = 7.6 times brighter. If the walls were white with a reflectivity of 85% the net Lux compared to the black-walled room might be (1.85)⁵ = 21.7 times brighter. [Note that the multiplier factor of 5, the exponent, is a guesstimate, and can itself vary a lot depending on the different reflectivities of the floor, the furniture, the net wall reflectivity, windows and doors, etc. -- SO there is no real way to calculate Lux without knowing very detailed information about your specific case. Which is why I usually say, for very complex situations where safety is a concern, "Hire a lighting engineer". In your case, get a lux meter, make some readings, and then make your calculations.

I just noticed I had transposed the terms in the 3rd sentence of the last paragraph. It should read as follows:

You'd get a Lux value as above, where you divide the total lumens by the room surface area.

Use DIALUX , YOu can compute all calculations..

Put simply YES you can estimate it without software but NO you can't do it without lumen outputs.

The method is called the Lumen Method, or more accurately the Zonal Cavity Index method. The IES website provides some instruction as to the application however basically:

1. Select a light fitting
2. Select a lamp source(-s) for this fitting which will yield lumen output
3. Apply a maintenance factor (MF) to allow for lumen depreciation and aging
4. Calculate Zonal Cavity Index (ZCI) according to size of room
5. Apply a Utilisation Factor (UF) from manufacturer's data for that fitting, with those lamps, in a room with ZCI, with certain reflectances of walls, floor & ceiling

Lux level can then be calculated by: no. of fittings x lamps x factors / area. So as you can see you require lumen output.

However this method can be best described as an approximation to give some idea of results. There are many other factors such as colour rendition, glare and uniformity to consider in lighting design. This is why software techniques (such as the freely available DIALUX) are necessary to produce accurate or meaningful results. The variables involved are enormous, as is the skill and knowledge required to ensure accuracy.

Some manufacturers websites (such as Zumtobel) have built-in calculators to guide you after you have selected a fitting. Thus you do not need to install DIALUX or similar. But only for that manufacturer of course ;-)