the clays when mixed with water acquire the property known as plasticity, which plays a key role during processing. the techniques used to characterize the plasticity often do not show quantitative results that allow its application in mathematical models of the forming process of clays. this study aimed to develop a mathematical model for calculating the average pressure of extrusion, evaluating the plasticity through compression tests. then, the theoretical results of the extrusion pressure were compared to experimental results and a good agreement was found between them. it was possible to observe a correlation between effective stress of compression and extrusion pressure. for the extrusion process modeling equation, the effective stress obtained by compression test was a significant parameter that reveals the behavior of the clay during processing.