The flow pattern of supercritical bend manholes can result very complex due to the possible occurrence of the choking flow condition. This failure condition limits the maximum discharge conveyable by a bend manhole. At a design stage, it is, therefore, convenient to know the maximum capacity of the inspected bend manhole geometry and compare it to the design discharge carried out by the approach pipe. The present paper aims to give to the practitioners an immediate design tool to estimate the hydraulic capacity of supercritical bend manhole and, consequently, select the best appropriate geometrical setup. This tool consists of an empirical equation, according to which the bend manhole capacity is computed as a function of axial curvature radius, the length of the straight extension at the end of the manhole, the bend angle and the approach partial filling ratio. The accuracy was proved by carrying out a detailed experimental campaign based on the utilization of a CFD 3D numerical model.