How to calculate manually the number of lighting fixtures needed for an area if more than one type of fixtures are used?
Is there any formula?
Well for a single type of fixture, there is the lumen-formula but I do not know if there is a combination of fixtures that can be used?

Is this for an office or commercial space?
This is something typically done by an engineer or lighting specialist.
Unless the fixture is a commercial fixture there will likely be no photometric data for it.

Can you please give the procedure?
Lets just think that the data is available...
And yes if the mounting height is not same then what has to be done?
What I mean to say is that, two types of fixtures and different mounting heights... how to calculate the numbers of lamps of each type?

Can you please give the procedure?
Lets just think that the data is available...
WHAT procedure?
And how can we pretend the data is available if it is not?? What numbers do you use?

I am very confused as to what it is you are looking for.
We do not even know what fixtures you are talking about. :confused:

Sorry for replying late... I was out of town...

Okay...
An outdoor area, I have used RVP302 and SWF 331 of philips in different heights and positions...
The software has calculated the output result...
What I am asking for is - the base-formula of the algorithm with which the software(lighting software - calculux area) has done all the calculations... If the same thing I have to do manually, then what will be the steps..

Are you designing a software program to do the calculations?

The type of information you are seeking is not information an electrician would deal with.

An electrician's involvement would be limited to making sure the power is adequate for the design.

The electrician would be working off a design specification for that immediate area.

There are power calculations per square foot, based on the type of venue to be lit, but these are power requirements, not lumen requirements.

None of your questions and responses really make any sense.

But in an effort to help you...

The software you have probably uses the lumen method basic formula is usually expressed as follows:


E=N x L x MF x AL x UF / A

Where E = average illuminance

N = number of lamps used in the installation

L = lighting design lamp lumens (the product of initial

lumens and lamp depreciation factor)

MF = maintenance factor

AL = factor to represent atmospheric absorption losses

UF = utilisation factor of floodlights

A = area to be lit by floodlights

And/or could be using the more accurate point by point method:

For planes perpendicular to the direction of candlepower (Inverse Square Law):

Footcandles (fc) = I ÷ D2

I = Candlepower in candelas (cd)

D = Direct distance between the lamp and the point where light level is calculated



Many workplanes are not perpendicular to the direction of light intensity, which is why calculating light level at a point is useful for such applications. In these cases, we often must determine light levels on workplanes that are not horizontal and perpendicular but tilted or even vertical. For tilted-horizontal or vertical planes:

Horizontal Footcandles (fch) = (I ÷ D2) x H

Vertical Footcandles (fcv) = (I ÷ D2) x L

I = Candlepower in candelas (cd)

D = Direct distance between the lamp and the point where light level is calculated

H = Distance between the lamp and the point direct below on the workplane

L = Distance between that point and the point where light level is being calculated

D = Square Root of (H2 + L2) or D2 = H2 + L2

You may consider looking at existing Installations, if for one project.
Lot of useful info above.
Parking Lot?