A global inventory of small floating plastic debris was conducted using the largest dataset of microplastic measurements to assess the confidence in global estimates of microplastic abundance and mass. The study used a statistical framework to standardize data from surface-trawling plankton nets and combined it with three ocean circulation models to spatially interpolate observations. The results show that in 2014, the accumulated number of microplastic particles ranged from 15 to 51 trillion, weighing between 93 and 236 thousand metric tons, which is approximately 1% of the global plastic waste estimated to enter the ocean in 2010. These estimates are larger than previous global estimates but vary widely due to data scarcity, model differences, and knowledge gaps about microplastic sources and fates. The study focused on small plastic debris (nominally <200 mm) on the ocean surface, as these are the most sampled and have biological impacts. Data were collected using plankton nets, with particle counts and mass reported. The study used a generalized additive model (GAM) to standardize data, accounting for sampling year, wind speed, and other variables. Three ocean circulation models were used to predict microplastic distribution, showing large variability in concentrations. The van Sebille model showed higher concentrations, possibly due to its source function. The results indicate that the highest concentrations are in subtropical gyres, with the North Pacific having the largest mass reservoir. The study highlights the need for more data, especially in undersampled regions, to improve understanding of microplastic distribution and impact. The findings suggest that microplastics are a significant but under-estimated component of ocean plastic pollution, with implications for marine ecosystems and global environmental policy.A global inventory of small floating plastic debris was conducted using the largest dataset of microplastic measurements to assess the confidence in global estimates of microplastic abundance and mass. The study used a statistical framework to standardize data from surface-trawling plankton nets and combined it with three ocean circulation models to spatially interpolate observations. The results show that in 2014, the accumulated number of microplastic particles ranged from 15 to 51 trillion, weighing between 93 and 236 thousand metric tons, which is approximately 1% of the global plastic waste estimated to enter the ocean in 2010. These estimates are larger than previous global estimates but vary widely due to data scarcity, model differences, and knowledge gaps about microplastic sources and fates. The study focused on small plastic debris (nominally <200 mm) on the ocean surface, as these are the most sampled and have biological impacts. Data were collected using plankton nets, with particle counts and mass reported. The study used a generalized additive model (GAM) to standardize data, accounting for sampling year, wind speed, and other variables. Three ocean circulation models were used to predict microplastic distribution, showing large variability in concentrations. The van Sebille model showed higher concentrations, possibly due to its source function. The results indicate that the highest concentrations are in subtropical gyres, with the North Pacific having the largest mass reservoir. The study highlights the need for more data, especially in undersampled regions, to improve understanding of microplastic distribution and impact. The findings suggest that microplastics are a significant but under-estimated component of ocean plastic pollution, with implications for marine ecosystems and global environmental policy.