This scoping note presents a high-level overview of the main approaches to, and challenges faced when, calculating product-level carbon intensity metrics, including those applicable to collecting and verifying information across the supply chain. Though the analysis focuses on approaches used in emissions-intensive trade-exposed sectors (EITE), the findings also have broader relevance to other sectors. As part of the analysis, challenges relating to computing sector-level carbon intensity metrics are also considered, particularly as inputs to product-level metrics.