In this work, the critical outlet widths (COWS) for continuous bulk solids flow predicted by Jenike's theory, the McLean correlation, Enstad's theory, and Finite Element Method (FEM) analysis are compared. The FEM predictions use a Mohr-Coulomb elasto-plastic constitutive model. Unlike Jenike's theory and the McLean correlation, Enstad's theory and the FEM model show that the COW depends on the material height. The effects of the material internal friction angle, slope of the flow function, wall friction angle, and hopper half angle on the COW predictions are explored. Comparisons to experimental COWs from the literature show that the FEM model provides, by far, the best predictions. The primary advantage of using an FEM model for COW predictions are that complex materials and hopper geometries may be simulated, where simplifying assumptions of the standard theoretical models are not valid. (C) 2019 Elsevier B.V. All rights reserved.