Full grain size distributions were compiled from over 30,000 sediment samples collected by national and European surveys between 1960 and 2014. The median grain size was determined at the 50% percentile of the cumulative distribution curves . Multivariate geostatistics (external drift kriging) was employed to spatially predict the median grain size content using information on the percentage mud content as a trend variable. Data provider: Research and Technology Centre, West Coast, Büsum, DE Federal Maritime and Hydrographic Agency, Hamburg, DE Senckenberg Marine Research, Wilhelmshaven, DE Helmholtz-Zentrum Geesthacht, Geesthacht, DE BioConsult SH GmbH & Co. KG, Husum, DE British Geological Survey, Edinburgh, UK Marine Scotland - Marine Laboratory, Aberdeen, UK Institute of Geology, Hamburg University, Hamburg, DE Royal Netherlands Institute for Sea Research, Texel, NL Geological Survey of the Netherlands, Utrecht, NL School of Ocean Sciences, Bangor University, Bangor, UK Centre for Environment, Fisheries and Aquaculture Science, Lowestoft, UK Geological Survey of Norway, Trondheim, NO Geological Survey of Denmark and Greenland, Copenhagen, DK Geological Survey of France, Orléans, FR Det Norske Veritas, Hørvik, NO Hamburg Port Authority, Hamburg, DE Project “Management, Research and Budgeting of Aggregates in Shelf Seas related to End-users” (2002-2006), Ghent University, BE Project “North Sea Benthos Survey 1986”, International Council for the Exploration of the Sea (ICES), Copenhagen, DK Project “North Sea Benthos Project 2000”, International Council for the Exploration of the Sea (ICES), Copenhagen, DK Project “Geopotential Deutsche Nordsee” (2009-2013), http://www.gpdn.de/ Management Unit of the North Sea Mathematical Models, Royal Belgian Institute of Natural Sciences, Brussels, BE