Cities bear a large burden of plastic management and pollution, which is not consistently recognized. The ‘circular economy’ has become an aspiration for reducing pollution and increasing sustainability, though quantification and monitoring methods are not consistent. We compare data from six cities participating in the Urban Ocean® program that utilized the Circularity Assessment Protocol (CAP) in India, Indonesia, Malaysia, Panama, and Vietnam. CAP is a standardized methodology used to quantify circular materials management and collect community-level data to inform decision-making. Results show that plastic items and packaging represent over 90% of fast-moving consumer goods, 78% of to-go items, and 69% of all litter items, presenting challenges to local formal and informal waste management systems. These results support solutions that meet an individual city's needs and reflect the materials and challenges present. City-level data facilitates knowledge exchange between communities, which can lead to an effective network of more circular cities worldwide.