Enter the visibility distance and light intensity into the calculator to determine the fog factor. This calculator helps to assess the level of fog and its impact on visibility.

Fog Factor Formula

The following formula is used to calculate the fog factor:

FF = V * sqrt(LI)


  • FF is the fog factor
  • V is the visibility distance (meters)
  • LI is the light intensity (candelas)

To calculate the fog factor, multiply the visibility distance by the square root of the light intensity.

What is a Fog Factor?

Fog factor is a measure used to quantify the level of fog in terms of visibility and light intensity. It is a useful metric for transportation safety, especially for drivers and pilots, to assess the potential impact of fog on travel conditions. A higher fog factor indicates better visibility conditions despite the presence of fog.

How to Calculate Fog Factor?

The following steps outline how to calculate the Fog Factor.

  1. First, determine the visibility distance (V) in meters.
  2. Next, determine the light intensity (LI) in candelas.
  3. Next, gather the formula from above = FF = V * sqrt(LI).
  4. Finally, calculate the Fog Factor (FF).
  5. After inserting the variables and calculating the result, check your answer with the calculator above.

Example Problem:

Use the following variables as an example problem to test your knowledge.

visibility distance (V) = 100 meters

light intensity (LI) = 250 candelas