Enter the plastic limit and the plasticity index into the Liquid Limit Calculator. The calculator will evaluate the Liquid Limit. 

Liquid Limit Formula

The following two example problems outline the steps and information needed to calculate the Liquid Limit.

LL  = PL - PI 


  • LL is the Liquid Limit ( )
  • PL is the plastic limit 
  • PI is the plasticity index 

To calculate the liquid limit, subtract the plasticity index from the plastic limit.

How to Calculate Liquid Limit?

The following steps outline how to calculate the Liquid Limit.

  1. First, determine the plastic limit. 
  2. Next, determine the plasticity index. 
  3. Next, gather the formula from above = LL  = PL – PI .
  4. Finally, calculate the Liquid Limit.
  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.

plastic limit = 43

plasticity index = 25

LL  = PL – PI  = ?