The Fermatean fuzzy set (FFS) is a type of fuzzy set that extends the concept of intuitionistic fuzzy sets. It is particularly useful for properly managing uncertainty while making decisions. The distance measures is a crucial tool for resolving decision-making challenges. This article emphasizes the limitations of the existing distance measures for FFSs. Specifically, it demonstrates that the existing distance measures are incapable of accurately categorizing unknown patterns alongside known patterns. Consequently, we propose a new distance measure for FFSs. In order to assess the efficacy of the proposed distance measures, we demonstrate its desired characteristics. However, to compute the distance measures, we use various numerical examples. The results of numerical examples demonstrate that the proposed distance measure effectively overcome the constraints of existing distance measures, where the existing distance measures for FFSs are unable to accurately categorize unknown patterns alongside known patterns.