Sedimentation of particulate slurries in industrial sedimentation ponds and laboratory-based batch settling tests is difficult to describe analytically. Understanding long-time settling behavior is of particular importance when extrapolating existing sedimentation data to predict the final extent and how long it will take. A simple analytical equation has been derived to describe the final stage of compression in batch settling. In addition, numerical methods for determining the equation parameters have been proposed and demonstrated. The validity of the analytical equation and the parameters determined has been verified by comparison with finite element predictions. This new knowledge has the potential to significantly reduce the computational time requirements of predicting longtime batch settling behavior. (c) 2005 American Institute of Chemical Engineers.