This resource provides a standardized framework to measure marine plastic leakage from products, companies, or countries through a life-cycle assessment (Marine Plastic Footprint). The value of a life-cycle assessment framework is compared to circularity approaches with respect to plastic. Calculation methods cover macroplastics leaking from mismanaged waste and microplastics (textile fibres, tyre dust, cosmetics, and production pellets). The source lays out a generic data set (e.g. loss rates) for the calculation of the Marine Plastic Footprint. Case studies demonstrate the ability to use this framework to prioritize interventions around plastic waste.