Flood Light Calculations - Brightness, Mounting Height, Spacing and Angle
In selecting a flood light, you will need to consider its brightness (measured in Lumens), mounting height, spacing and angle.
Brightness (Lumens)
A general guideline for the brightness of the flood light is as follows:
- For a single area such as a park bench: 1,600-2,000 lumens
- For a small area such as a footpath: 2,000-3,700 lumens
- For a small yard: 6,000-8,000 lumens
- For a driveway: 8,000-10,000 lumens
- For a small parking lot: 13,500 lumens
- For a large parking lot: 20,000 lumens
- For a small road: 31,000 lumens
- For a wide road: 40,000 lumens
- For stadiums and highways: 50,000 lumens
A very general formula that can be used for security lighting is
Lumens = Area (in square meters) x 200
which would provide approximately the same amount of illumination as an office.
For example: the lumens required for a space 10m x 10m = 10 x 10 x 200 = 20,000 lumens
Mounting Height
The mounting height of the flood light should be half the distance being illuminated.
For example: if a flood light has to light a space which is 15m long then it should be mounted 7.5m high.
Spacing
When more than one flood light is required, then the space between each flood light should be 3 times their mounting height.
For example: if a road is being lit and the flood lights are mounted 8m high, then each flood light should be 24m apart.
Angle
The flood light should be aimed at a point 2/3 of the distance being illuminated.
For example: if the flood light has to light a space which is 15m long then it should be aimed at a point in the ground 10m away.