This document specifies the laboratory determination of the water (moisture) content of a soil test specimen by oven-drying within the scope of the geotechnical investigations according to prEN 1997-1 and prEN 1997-2. The water content is required as a guide to classification of natural soils and as a control criterion in re-compacted soils and is measured on samples used for most field and laboratory tests. The oven-drying method is the definitive procedure used in usual laboratory practice. The practical procedure for determining the water content of a soil is to determine the mass of water removed by drying the moist soil (test specimen) to a constant mass in a drying oven controlled at a given temperature, and to use this value as the mass of water in the test specimen related to the mass of solid particles. The mass of soil remaining after oven-drying is used as the mass of the solid particles.