In a constantly evolving global market, manufacturing companies need to be flexible and adaptive to survive. Digital twins of production systems have been proposed as one part of the solution, however this comes with multiple challenges. Manufacturing SMEs have limited resources and need to direct their efforts in this area wisely. This paper presents a tool for holistic assessment of an SME manufacturer's level of digitalization, in order to visualize current gaps and guide digitalization efforts over a production system's life cycle. The tool was empirically developed together with Manufacturing SMEs and has strengthened their digitalization awareness and capabilities. © 2020 The Authors.