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Gross register tonnage

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This article is about a historic measure of a ship's internal volume, since superseded. It is not to be confused with deadweight tonnage or displacement (ship).

Gross register tonnage (GRT, grt, g.r.t., gt) or gross registered tonnage, is a ship's total internal volume expressed in "register tons", each of which is equal to 100 cubic feet (2.83 m3). Replaced by Gross Tonnage (GT), gross register tonnage uses the total permanently enclosed capacity of the vessel as its basis for volume. Typically this is used for dockage fees, canal transit fees, and similar purposes where it is appropriate to charge based on the size of the entire vessel. Internationally, GRT may be abbreviated as BRT for the German "Bruttoregistertonne".

Net register tonnage subtracts the volume of spaces not available for carrying cargo, such as engine rooms, fuel tanks and crew quarters, from gross register tonnage.[1][2]

Gross register tonnage is not a measure of the ship's weight or displacement and should not be confused with terms such as deadweight tonnage or displacement.

Discover more about Gross register tonnage related topics

Net register tonnage

Net register tonnage

Net register tonnage is a ship's cargo volume capacity expressed in "register tons", one of which equals to a volume of 100 cubic feet (2.83 m3). It is calculated by subtracting non-revenue-earning spaces i.e. spaces not available for carrying cargo, for example engine rooms, fuel tanks and crew quarters, from the ship's gross register tonnage. Net tonnage is thus used in situations where a vessel's earning capacity is important, rather than its mere size. Net register tonnage is not a measure of the weight of the ship or its cargo, and should not be confused with terms such as deadweight tonnage or displacement.

Deadweight tonnage

Deadweight tonnage

Deadweight tonnage or tons deadweight (DWT) is a measure of how much weight a ship can carry. It is the sum of the weights of cargo, fuel, fresh water, ballast water, provisions, passengers, and crew.

Displacement (ship)

Displacement (ship)

The displacement or displacement tonnage of a ship is its weight. As the term indicates, it is measured indirectly, using Archimedes' principle, by first calculating the volume of water displaced by the ship, then converting that value into weight. Traditionally, various measurement rules have been in use, giving various measures in long tons. Today, tonnes are more commonly used.

History

Further information: Gross tonnage and Net tonnage

Gross register tonnage was defined by the Moorsom Commission in 1849. Gross and net register tonnages were replaced by gross tonnage and net tonnage, respectively, when the International Maritime Organization (IMO) adopted The International Convention on Tonnage Measurement of Ships on 23 June 1969. The new tonnage regulations entered into force for all new ships on 18 July 1982, but existing vessels were given a migration period of 12 years to ensure that ships were given reasonable economic safeguards, since port and other dues are charged according to ship's tonnage.

Since 18 July 1994 the gross and net tonnages, dimensionless indices calculated from the total moulded volume of the ship and its cargo spaces by mathematical formulae, have been the only official measures of the ship's tonnage.[3] However, the gross and net register tonnages are still widely used in describing older ships.

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Gross tonnage

Gross tonnage

Gross tonnage is a nonlinear measure of a ship's overall internal volume. Gross tonnage is different from gross register tonnage. Neither gross tonnage nor gross register tonnage should be confused with measures of mass or weight such as deadweight tonnage or displacement.

Net tonnage

Net tonnage

Net tonnage is a dimensionless index calculated from the total moulded volume of the ship's cargo spaces by using a mathematical formula. Defined in The International Convention on Tonnage Measurement of Ships that was adopted by the International Maritime Organization in 1969, the net tonnage replaced the earlier net register tonnage (NRT) which denoted the volume of the ship's revenue-earning spaces in "register tons", units of volume equal to 100 cubic feet (2.83 m3). Net tonnage is used to calculate the port duties and should not be taken as less than 30 per cent of the ship's gross tonnage.

Moorsom System

Moorsom System

The Moorsom System is a method created in the United Kingdom of calculating the tonnage or cargo capacity of sailing ships as a basis for assessing harbour and other vessel fees. It was put into use starting in 1849 and became British law in 1854.

International Maritime Organization

International Maritime Organization

The International Maritime Organization is a specialised agency of the United Nations responsible for regulating shipping. The IMO was established following agreement at a UN conference held in Geneva in 1948 and the IMO came into existence ten years later, meeting for the first time in 1959. Headquartered in London, United Kingdom, IMO currently has 175 Member States and three Associate Members.

Source: "Gross register tonnage", Wikipedia, Wikimedia Foundation, (2023, February 17th), https://en.wikipedia.org/wiki/Gross_register_tonnage.

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Further Reading

Passenger ship

Deadweight tonnage

Gross tonnage

IMO number

Displacement (ship)

Net tonnage

List of large sailing vessels

Mafuta (ship)

RS Mistral

Rio Bravo (ship)

Rio de la Plata (ship)

Rio de Janeiro (2008 ship)

Monte Tamaro (ship)

Monte Azul (ship)
See also
References
  1. ^ Stopford, Martin (2009), Maritime Economics, Taylor & Francis, p. 752, ISBN 9780415275576, retrieved 2011-10-17
  2. ^ "Units and Systems of Measurement Their Origin, Development, and Present Status" (PDF). National Institute of Standards and Technology. Archived from the original (PDF) on 19 October 2011. Retrieved 17 October 2011.
  3. ^ International Convention on Tonnage Measurement of Ships Archived 2013-12-02 at the Wayback Machine. International Maritime Organization (IMO). Retrieved 2011-10-17.
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