# Plastic Index

Plastic index, abbreviated as PI, also called plasticity index, a dimensionless number, is the water content at which the soil changes from semi-solid state to solid state.

## plastic Index formula

\(\large{ PI = LL - PL }\) |

### Where:

Units |
English |
Metric |

\(\large{ PI }\) = plastic index | \(\large{dimensionless}\) | |

\(\large{ LL } \) = liquid limit | \(\large{dimensionless}\) | |

\(\large{ PL } \) = plastic limit | \(\large{dimensionless}\) |

Tags: Liquid Equations Soil Equations Geotechnical Equations