The article examines the process of digital transformation of machine-building companies in Russia. A brief overview of digital transformation studies conducted in Russia is presented. It is concluded that these studies are still of an overview and informational nature; the conducted studies lack a methodology for measuring the achieved digital maturity. The approaches to the studies of digital maturity carried out by foreign researchers are considered. It is noted that the use of foreign developments in Russia has limitations associated with the lack of necessary statistical information and the specific features of the organization of mechanical engineering. The authors revealed the relationship between marketing processes, total quality management and digitalization. A methodology for calculating the digital maturity index of a company has been developed, taking into account the specifics of the industry under study and the characteristics of the Russian economy. A quantitative assessment of the digital maturity of a number of engineering companies has been carried outfit is concluded that most companies in the industry have low to moderate digital maturity.