Enter the total flame distance (ft) and the total time (hrs) into the Calculator. The calculator will evaluate the Chains Per Hour. 

Chains Per Hour Formula

CPH = FD/66/T


  • CPH is the Chains Per Hour (chains/hour)
  • is the total flame distance (ft)
  • is the total time (hrs)

To calculate Chains Per Hour, divide the flame distance in feet by 66, then divide by the total time.

How to Calculate Chains Per Hour?

The following steps outline how to calculate the Chains Per Hour.

  1. First, determine the total flame distance (ft). 
  2. Next, determine the total time (hrs). 
  3. Next, gather the formula from above = CPH = FD/66/T.
  4. Finally, calculate the Chains Per Hour.
  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.

total flame distance (ft) = 12

total time (hrs) = 2

Frequently Asked Questions (FAQ)

What is a “chain” in the context of measuring flame distance?

A chain is a unit of length that is typically used in surveying and forestry. It is equivalent to 66 feet or 20.1168 meters. In the context of measuring flame distance, it refers to the length of the flame front.

Why is the number 66 used in the Chains Per Hour formula?

The number 66 is used in the Chains Per Hour formula because one chain equals 66 feet. This conversion factor is necessary to calculate the speed of the flame front in chains per hour, based on the distance it travels in feet.

How can the Chains Per Hour calculation be useful in firefighting or controlled burns?

Calculating the Chains Per Hour can help firefighters and land managers estimate the speed at which a fire is spreading. This information is crucial for making strategic decisions about resource allocation, evacuation, and containment efforts during wildfires or in planning controlled burns.

Can the Chains Per Hour formula be used for any type of fire?

While the Chains Per Hour formula provides a general estimation of fire spread speed, its accuracy can vary depending on the type of fire, terrain, and weather conditions. It is most useful for surface fires in open areas and may need adjustments or different models for crown fires, complex terrain, or highly variable fuel types.