Deadweight tonnage is a measure of a vessel's weight carrying capacity, not including the empty weight of the ship. It is distinct from the
displacement (weight of water displaced), which includes the ship's own weight, or the volumetric measures of
gross tonnage or
net tonnage (and the legacy measures
gross register tonnage and
net register tonnage). Deadweight tonnage was historically expressed in
long tons, but is now usually given internationally in
tonnes (metric tons). In modern international shipping conventions such as the
International Convention for the Safety of Life at Sea and the
International Convention for the Prevention of Pollution From Ships, deadweight is explicitly defined as the difference in tonnes between the displacement of a ship in water of a
specific gravity of 1.025 (corresponding to average density of
sea water of ) at the
draft corresponding to the assigned
summer freeboard and the
light displacement (lightweight) of the ship. == See also ==