In this study, a methodology is proposed for evaluating the dependability measures of Industrial Internet of Things (IIoT) systems, incorporating assessment of hardware, network components, and software. The existing practical methods for assessing the dependability of IIoT systems, along with their respective strengths and limitations, are presented and critically analyzed. Based on the obtained data, an enhanced method for multifactor forecasting of the dependability measures of IIoT systems is developed and described. An IDEF0 diagram of this method is constructed, and a table with numerical values of availability factors is presented, considering various types of modulation and topologies.