DEADWEIGHT/DWAT/DWCC- A common measure of ship carrying capacity. The
number of tons (2240 lbs.) of cargo, stores and bunkers that a vessel can transport.
It is the difference between the number of tons of water a vessel displaces "light"
and the number of tons it displaces "when submerged to the 'deep load line'." A
vessel's cargo capacity is less than its total deadweight tonnage. The difference in
weight between a vessel when it is fully loaded and when it is empty (in general
transportation terms, the net) measured by the water it displaces. This is the most
common, and useful, measurement for shipping as it measures cargo capacity.
NET TONNAGE- Equals gross tonnage minus deductions for space occupied by
crew accommodations, machinery, navigation equipment and bunkers.It
represents space available for cargo (and passengers). Canal tolls are based on net
(registered) tonnage.
Everyone who has looked at specifications for steamships is often bewildered by the
many different tonnages used for the same vessel. An ocean liner may have different
gross tonnage, depending on which country's rules were used in determining the
weight. Below is an article from 1932 that provides a good explanation on just what
the tonnages for ships really are.
There are five kinds of tonnage in use in the shipping business.
They are:
1.
2.
3.
4.
5.
Deadweight,
Cargo,
Gross,
Net and
Displacement Tonnages
Tonnage Defined
1. Deadweight Tonnage: expresses the number of tons of 2,240 pounds that a
vessel can transport of cargo, stores, and bunker fuel. It is the difference
between the number of tons of water a vessel displaces "light" and the
number of tons it displaces when submerged to the "load line." Deadweight
tonnage is used interchangeably with deadweight carrying capacity. A
vessel's capacity for weight cargo is less than its total deadweight tonnage.
2. Cargo Tonnage: is either "weight" or "measurement." The weight ton in the
United States and in British countries is the English long or gross ton of 2,240
pounds. In France and other countries having the metric system a weight ton
is 2,204.6 pounds. A "measurement" ton is usually 40 cubic feet, but in some
instances a larger number of cubic feet is taken for a ton. Most ocean package
freight is taken at weight or measurement (W/M) ship's option.
3. Gross Tonnage: applies to vessels, not to cargo. It is determined by dividing
by 100 the contents, in cubic feet, of the vessel's closed-in spaces. A vessel
ton is 100 cubic feet. The register of a vessel states both gross and net
tonnage.
4. Net Tonnage: is a vessel's gross tonnage minus deductions of space occupied
by accommodations for crew, by machinery, for navigation, by the engine
room and fuel. A vessel's net tonnage expresses the space available for the
accommodation of passengers and the stowage of cargo. A ton of cargo in
most instances occupies less than 100 cubic feet; hence the vessel's cargo
tonnage may exceed its net tonnage, and, indeed, the tonnage of cargo carried
is usually greater than the gross tonnage.
5. Displacement: of a vessel is the weight, in tons of 2,240 pounds, of the vessel
and its contents. Displacement "light" is the weight of the vessel without
stores, bunker fuel, or cargo. Displacement "loaded" is the weight of the
vessel plus cargo, fuel, and stores.
For a modern freight steamer the following relative tonnage figures would
ordinarily be approximately correct:




Net tonnage 4,000
Gross tonnage 6,000
Deadweight carrying capacity 10,000
Displacement, loaded, about 13,350
Registered Tonnage
A vessel's registered tonnage, whether gross or net, is practically the same under
the American rules and the British rules. When measured according to the Panama
or Suez tonnage rules most vessels have larger gross and net tonnages than when
measured by British or American national rules.
Source: Article appearing in the American Export Lines, Passenger List from June 28,
1932.
Read more: Ship Tonnage Explained - Deadweight, Cargo, Gross, Net,
Displacement http://www.gjenvick.com/SteamshipArticles/ShipTonnage/1932-0628-ShipTonnageExplained.html#ixzz41HpOh0mV
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Definition of 'Gross Registered Tonnage'
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GRT is the volume of space within the hull and enclosed space above the deck of a
merchant ship which are available for cargo, stores, fuel, passengers and crew.
Definition: Gross Registered Tonnage (GRT) is the volume of space within the hull
and enclosed space above the deck of a merchant ship which are available for cargo,
stores, fuel, passengers and crew.
Description: Gross Registered Tonnages are actually measurements of cubic
capacity.
Gross tonnage is measured according to the law of the national authority with which
the ship is registered. The measurement is, broadly, the capacity in cubic feet of the
spaces within the hull and of the enclosed spaces above the deck available for cargo,
stores, passengers and crew, with certain exceptions, divided by 100. Thus 100
cubic feet of capacity is equivalent to one gross ton. The GRT is on decline in India.
The data pulled from the government sources indicate the decline in the national
tonnage from almost 7 million GRT to 6.39 million GRT.
Net Tonnage: Net tonnage is derived from gross tonnage by deducting spaces used
for the accommodation of crew, navigation machinery and fuel. Gross or Net
tonnage are usually the basis on which Port dues are charged. Naval architects are
adept at building ships which can carry cargo in spaces not included in the tonnage.
Deadweight Tonnage: Deadweight is the weight of cargo, crew passengers and
stores that a ship can carry. It is the difference between light and loaded
displacement. It is a measure expressed in metric tons (1,000 kg) or long tons
(1,016 kg) of a ship's carrying capacity, including bunker oil, fresh water, crew and
provisions. It is the most important commercial measure of the capacity.