Tonnage is a measure of the size or cargo carrying capacity of a ship. Various types of tonnages are there as per the tonnage convention.

1. Elements of Shipping
Management
- Ship’s Tonnages
- Ajith V A
MBA ITLM
IMU Cochin

2. TONNAGE
▸Tonnage is a measure of the size or cargo carrying capacity of a ship.
▸A commonly defined measurement system is important; since a ship’s
registration fee, harbour dues, safety and manning rules etc., are based on its
gross tonnage (GT) or net tonnage (NT).
▸The Tonnage Convention 1994 (1969) was adopted at a conference held
under the auspices of the IMO to introduce a universally recognized system for
measuring the tonnage of ships.
▸“Tonnage” specifically refers to a calculation of the volume or cargo volume
of a ship.
▸Tonnage should not be confused with Displacement which refers to the
loaded or empty weight of the vessel itself.
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3. Tonnage measurements :
There are five kinds of tonnage in use in the shipping
business.
They are:
▸ Deadweight
▸ Cargo,
▸ Gross,
▸ Net and
▸ Displacement Tonnages
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4. Lightweight tonnage
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▸ Lightweight tonnage is best described as the weight of the ship when it was built
in the shipyard including all framing, machinery, decking etc.
▸It does not include the weight of any consumables such as fuel, water, oil or
supplies.

5. Deadweight tonnage
▸It is a measure of how much weight a ship can safely carry.
▸It is the sum of the weight of cargo, fuel, fresh water, ballast water, provisions,
passengers and crew.
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6. Cargo tonnage
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▸It is the goods or produce transported for commercial gain by the ship.
▸Cargo tonnage is expressed in terms of a weight or measurement.

7. Gross registered tonnage
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▸Gross tonnage applies to vessels, not to cargo.
▸Gross tonnage (GT) is a function of the volume of ship's all enclosed spaces (from
keel to funnel) measured to the outside of the hull framing.

8. Net registered tonnage
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▸Net tonnage (NT) is based on a calculation of the volume of all cargo spaces of
the ship.
▸It indicates a vessel’s earning space and is a function of the molded volume of all
cargo spaces of the ship.

9. Displacement tonnage
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▸The displacement tonnage of a ship is the ship's weight.
▸The name reflects the fact that it is measured indirectly, by first calculating the
volume of water displaced by the ship, and then calculating the weight of that water.

10. Standard Displacement tonnage
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▸Standard displacement tonnage is basically same as displacement tonnage with
one minor difference.
▸When calculating standard displacement tonnage, you subtract the weight of any
fuel and potable water carried on board the ship.

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