Swelling soils which cause problems in geotechnical engineering necessitate their determination and taking convenient cautions before design studies. Determination of swelling soils by indirect methods is mostly preferred due to its quick and economical aspects. One of the most common used indirect methods of determining swelling soils is the swell potential chart proposed by Van Der Merwe. However, because of the factors affecting plasticity index and clay fraction values, some uncertainties can arise in classification of swelling soils when using this approach. The uncertainty level reaches its maximum when the evaluation points on the chart fall on the lines that separate certain classes or very close to these lines. In this study, a fuzzy classification process for the Van Der Merwe method was suggested in order to minimize these uncertainties. For the purpose of the study, the spatial distances of the points from the lines were taken into consideration. Fuzzy swell potential classes were obtained by using sigmoid functions and fuzzy operators. The suggested method was applied on a set of data acquired from the laboratory and the results were discussed at the end of the study.