This study provides a comprehensive assessment of the global abundance and distribution of small floating plastic debris in the ocean. Using the largest dataset of microplastic measurements to date, the authors standardized the data and spatially interpolated it using three different ocean circulation models. The results show that the accumulated number of microplastic particles in 2014 ranges from 15 to 51 trillion particles, weighing between 93 and 236 thousand metric tons, which is only about 1% of the global plastic waste estimated to enter the ocean in 2010. The estimates are larger than previous global estimates but vary widely due to data scarcity, differences in model formulations, and knowledge gaps about the sources, transformations, and fates of microplastics in the ocean. The study highlights the need for more data, especially in the Southern Hemisphere, and emphasizes the importance of understanding the full suite of impacts of plastic debris on marine ecosystems.This study provides a comprehensive assessment of the global abundance and distribution of small floating plastic debris in the ocean. Using the largest dataset of microplastic measurements to date, the authors standardized the data and spatially interpolated it using three different ocean circulation models. The results show that the accumulated number of microplastic particles in 2014 ranges from 15 to 51 trillion particles, weighing between 93 and 236 thousand metric tons, which is only about 1% of the global plastic waste estimated to enter the ocean in 2010. The estimates are larger than previous global estimates but vary widely due to data scarcity, differences in model formulations, and knowledge gaps about the sources, transformations, and fates of microplastics in the ocean. The study highlights the need for more data, especially in the Southern Hemisphere, and emphasizes the importance of understanding the full suite of impacts of plastic debris on marine ecosystems.