Microplastics in Ocean Calculator

Microplastics are plastic fragments smaller than 5 millimeters. They enter the ocean through mismanaged land-based waste (littering, open dumping), stormwater runoff, and the breakdown of larger plastic debris. Rivers are a major pathway, transporting terrestrial plastic into marine environments. See also our calculate Whale Carbon.

The ocean delivery rate is the percentage of mismanaged plastic waste that ultimately reaches the ocean. Research estimates this at roughly 1–8% depending on proximity to coastlines, drainage infrastructure, and local environmental conditions. A typical global estimate is around 3%.

Scientists measure microplastic concentration in particles per cubic meter (particles/m³) or milligrams per cubic meter (mg/m³) of seawater. Samples are typically collected with trawl nets or water column sampling, then filtered and analyzed under microscopy. The NOAA Laboratory Methods Manual outlines standardized procedures for this analysis.

AOMI is a global database of surface microplastic monitoring data contributed by researchers, institutes, and governments worldwide. It provides 2D maps of survey points and particle density distributions. Named after the Japanese term for 'blue ocean,' it supports international efforts to track and understand marine plastic pollution. You might also find our Marine Debris Impact Calculator useful.

Estimates suggest there are over 170 trillion microplastic particles currently floating in the world's oceans, with total mass estimates ranging from 1.5 to 12.7 million metric tons depending on the methodology and ocean layers considered. The numbers grow each year as plastic production continues to rise.

Because microplastics vary enormously in size — from sub-millimeter fibers to 5mm pellets — the assumed average particle mass dramatically changes the estimated particle count. A smaller average mass means each kilogram of plastic breaks into far more individual particles, increasing the estimated concentration significantly.

The degradation factor represents the proportion of plastic that remains intact over the accumulation period. In cold, deep water, plastics break down very slowly (high persistence). In warm, UV-exposed tropical surface water, plastics fragment more quickly. A factor of 0.7 means 70% of the original plastic mass persists as countable particles.

Yes — by adjusting the water body volume to match your target environment (river segment, lake, coastal zone), the calculator can estimate microplastic concentration in any water body. Just ensure your ocean delivery rate and other assumptions reflect that specific environment rather than open-ocean conditions.