As is known, the liquid limit has been used worldwide as an index test for a quick consistency characterization of clayey soils, as it is easy and inexpensive to determine. Consistency is a result of the hydrophilic and cohesive nature of clays caused by the adsorbed water surrounding the clay particles. Cation exchange capacity is a parameter that is affected by the type of clay mineral, and there is a relationship between cation exchange capacity and liquid limit. However, there is no clearly defined quantitative relation between them. In this study, fine-grained soil samples have been collected from various locations and tested. The tests include determination of cation exchange capacity and liquid limit. The parameters obtained were correlated, and a regression equation established showing a high coefficient of correlation (R = 0.97). Finally, a classification and Swelling potential chart for clayey soils is suggested based on the cation exchange capacity and the liquid limit.