Soil plasticity fundamentals covering the deformation behavior of clay-rich soils without cracking or volume loss, governed by water content and clay mineral structure. The diagram maps four soil consistency states—solid, semi-solid, plastic, and liquid—and their transitions via Atterberg limits (LL, LP, LC) determined by ASTM D4318 laboratory testing. Plasticity Index (IP = LL − LP) and Liquidity Index (IL) quantify soil compressibility and current consistency, enabling engineers to predict settlement, liquefaction risk, and construction suitability. Fork this flowchart to customize for regional soil classifications, add site-specific test data, or embed in geotechnical reports and course materials. The practical example (LL 68.40%, LP 22.71%, IP 45.69%) demonstrates high-plasticity clay behavior critical for foundation design.