Enter the total annular volume (bbls) and the total flow rate (bbl/min) into the Lag Time Calculator. The calculator will evaluate the Lag Time. 

Lag Time Formula

The following two example problems outline the steps and information needed to calculate the Lag Time.

LT = AV / FR


  • LT is the Lag Time (min)
  • AV is the total annular volume (bbls) 
  • FR is the total flow rate (bbl/min) 

To calculate the lag time, divide the annular volume by the total flow rate.

How to Calculate Lag Time?

The following steps outline how to calculate the Lag Time.

  1. First, determine the total annular volume (bbls). 
  2. Next, determine the total flow rate (bbl/min). 
  3. Next, gather the formula from above = LT = AV / FR.
  4. Finally, calculate the Lag Time.
  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 annular volume (bbls) = 50

total flow rate (bbl/min) = 20

LT = AV / FR = ?