Deadweight tonnage (also known as deadweight; abbreviated to DWT, D.W.T., d.w.t., or dwt) or tons deadweight (DWT) is a measure of how much
weight a ship can carry.
It is the sum of the weights of
cargo
Cargo consists of bulk goods conveyed by water, air, or land. In economics, freight is cargo that is transported at a freight rate for commercial gain. ''Cargo'' was originally a shipload but now covers all types of freight, including tra ...
, fuel,
fresh water,
ballast water, provisions, passengers, and
crew.
DWT is often used to specify a ship's maximum permissible deadweight (i.e. when it is fully loaded so that its
Plimsoll line is at water level), although it may also denote the actual DWT of a ship not loaded to capacity.
Definition
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
[One long ton (LT) is ] but is now usually given internationally in
tonne
The tonne ( or ; symbol: t) is a unit of mass equal to 1000 kilograms. It is a non-SI unit accepted for use with SI. It is also referred to as a metric ton to distinguish it from the non-metric units of the short ton ( United State ...
s (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
Relative density, or specific gravity, is the ratio of the density (mass of a unit volume) of a substance to the density of a given reference material. Specific gravity for liquids is nearly always measured with respect to water at its dens ...
of 1.025 (corresponding to average density of
sea water) at the
draft corresponding to the assigned
summer freeboard and the
light displacement (lightweight) of the ship.
See also
*
Notes
References
{{DEFAULTSORT:Deadweight Tonnage
Nautical terminology
Ship measurements
Shipbuilding