In this paper a fast, practical maximum loading point (MLP) calculation method is presented. The calculation process is based on the properties of the normal vector to the feasibility boundary computed close to MLP, which is calculated through a load flow method with step size optimization (LFSSO). Moreover, a practical procedure is added to the overall calculation process to include the operator's information on the acceptable error in the final result. The basic process is characterized by obtaining consecutive approximations of the MLP within the infeasible region. In each step, a correction factor based on the maximum admitted error in the final MLP is applied. Reactive power generation limits are taken into account. The MLP is accurately obtained after just a few steps, demonstrating the efficiency of the proposed method. Simulation results for IEEE test and realistic systems are shown to validate the proposed method. ©2010 IEEE.