This paper describes a methodology for calculating a Material Circularity Indicator for manufactured products and companies. 
The prime purpose of this paper is to describe the thinking behind the methodology, alongside a derivation of the equations that lead to the calculation of the Material Circularity Indicator.
In addition to this methodology, a Circularity Indicators tool has been developed by Granta Design Ltd. and integrated with the MI:Product Intelligence package, which enables users to analyze and evaluate a range of environmental, regulatory and supply chain risks for their designs and products via a browser application, MI:BoM Analyzer.8 The tool uses the product-level comprehensive approach and encompasses a number of complementary indicators. This tool will be available under commercial terms. As part of the project, the Ellen MacArthur Foundation has provided an easy to use Excel-based model to illustrate the functioning of the methodology on the product level. This is downloadable from the Circularity Indicator Project website9 and is intended to be useful for people interested to see how the various parameters in the methodology interact with each other.
As part of the project, the methodology has been tested by a group of pilot companies using real product data. Testing was an iterative process running through five test phases and included in-person and virtual workshops. The pilot companies are listed in Appendix F.1.
In addition, several other stakeholders from investors, regulators, consultancies, and universities were involved in the project through workshops held in London to discuss the approach taken and to seek input into expected use cases. In total, stakeholders from about 30 organizations attended the workshops, many attending more than one and with several delegates. This paper has also been through two detailed peer review phases by an expert panel of reviewers.