The scientific literature shows that since 1982 several rational retention criteria for geotex-tile filters have been suggested by different authors, involving diverse parameters and considerations. Few, however, incorporate the existing number of constrictions in the geotextile manufactured plan, an important parameter that affects the path through which a soil particle travels. The focus of this work is aimed at delineating and discussing three rational analyses that comprise the calculation of the number of constrictions in nonwoven geotextile filters. For each analysis, the boundary conditions used to build the theoretical methods are described. A case study is then presented to provide a better insight as to how the number of constrictions varies according to each approach. It becomes evident that, because two of the analyzed propositions are essentially probabilistic, they may return an estimation of the number of con-strictions necessary to retain a defined soil particle, while the third one returns the total number of con-strictions inherently present in a geotextile. Thus, a comparison between the three methods is only possi-ble if the number of constrictions according to those probabilistic approaches is calculated by means of computing the ratio between the geotextile thickness and the inter-constriction distance, which in turn varies from one approach to the other. Significant discrepancies among the results from all three methods were found.