Step 2: Determine square footage of area to be lighted (length x width).

Step 3: Determine type of fixture to be used and proper mounting height.

Step 4: Identify initial lumens of fixture type (sese product description)

Step 5: Determine dirt depreciation factor of fixture from Light Depreciation Chart below.

Step 6: Use formula with above data to calcualte number of fixtures.

Formula:

Number of fixtures = 3 x number of footcandles needed x sq. footage of area divided by initial lumens of fixture (lamp) type x dirt depreciation.

 

Example:

Using 400 watt hps on 30' pole. 3 x 2 x 40,000 divided by 50,000 x 1.01 = 4.85. (All fractions should be rounded off.) Required number of fixtures = 5.

 

Note: This is not a precise lighting guide.