The Material Circularity Index (MCI) is a metric used to measure the circularity of materials in a product or system. It quantifies the extent to which materials are reused, recycled, or recovered at the end of their life cycle, rather than being discarded as waste. The MCI provides a numerical value that reflects the percentage of recycled or reused materials in relation to the total materials used. A higher MCI indicates a higher level of circularity and a more sustainable approach to material use.