# 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

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