# Liquid Index

Written by Jerry Ratzlaff on . Posted in Geotechnical Engineering

Liquid index, abbreviated as LI, also called liquidity index, a dimensionless number, is scaling the natural moisture content of a soil sample to the liquid limit and plastic limit.

## Liquid Index formula

 $$\large{ LI = \frac{ PL \;-\; w_n }{ LL \;-\; PI } }$$

### Where:

 Units English Metric $$\large{ LI }$$ = liquid index $$\large{dimensionless}$$ $$\large{ LL }$$ = liquid limit $$\large{dimensionless}$$ $$\large{ w_n }$$ = natural water content (moisture content) $$\large{dimensionless}$$ $$\large{ PI }$$ = plastic index $$\large{dimensionless}$$