The sufficiently accurate prediction of loading limits is essential for the design of conventional structured packings and sandwich packings, in which a countercurrent flow of two phases takes place. Based on the so-called Wallis plot, an empirical approach to the determination of the flooding point can be suggested. In this work, the Wallis equation is extended using experimentally estimated loading limits of structured packings as well as sandwich packings. The influence of different parameters on loading limits is considered in the proposed correlation. The Wallis equation is implemented into a fluid dynamic model for the description of the pressure drop of sandwich packings.