Determination of the mass of material subject to IAEA safeguards verification, such as solid materials or solutions in containers and solutions in tanks. For materials where only volume measurement is possible, the mass can be calculated by using the measured density of the material. In the context of IAEA safeguards, bulk measurement is necessary in connection with sampling and is done just before samples are taken. The sample related bulk data collected on-site by the IAEA inspector concomitantly with the sampling include the mass (or volume and density) of the sampled items or batches as declared by the facility operator and verified by the inspector.