The ASTM D 2487 soil classification system, an ASTM adaptation of the Unified Soil Classification System (USCS), categorizes mineral and organo-mineral soils for engineering purposes based on particle-size distribution, liquid limit, and plasticity index.
The USCS Calculator allows you to determine the soil group name and symbol from your field data, for use in soil descriptions when preparing boring and test pit logs. For more information, you can refer to the official USCS guidelines provided in this PDF document.