Contemporary societies, whether they have reached advanced levels of economic and social development or are still developing, need to prioritise the implementation of circular economy practices. This will facilitate the shift towards regenerative, sustainable, and closed-loop industrial systems. For now, there are some efforts to encourage patterns of production and consumption through changes in economic trends, development of institutional frameworks, harmonising regulations in the field of environmental protection, and raising the level of social awareness to achieve, above all, greater efficiency of resources. Extensive literature that deals with monitoring the implementation of the circular economy already indicates the existence of numerous barriers in this process but also notices some incentives for raising the degree of circularity of the observed systems. In this paper, the question of whether a single value can represent the level of circularity of the chosen material/product chain is researched. An overview of barriers and drivers for implementing circular economy strategies is given to structure a proper metric framework in correlation to the research question. The objective was to simplify the monitoring of circularity by developing a unique index for comparing material/product chains in similar systems. This was accomplished by using the circular material use (CMU) rate introduced in the European Union and modifying it for financial data calculation. As a result, the circular economy index, which covers all 9R strategies (CEIR), is obtained. The practical verification of model applicability was shown by determining the degree of circularity achieved for passenger cars in the four observed EU countries.
