By Kevin Joseph
MBA (Energy Trading)
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.
Tonnage is a measure of the size or cargo carrying
capacity of a ship.
“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.
Tonnage measurements :
There are five kinds of tonnage in use in the shipping business.
Dead weight 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
Cargo : it is the goods or produce
transported for commercial gain by
Gross tonnage (GT) is a function of
the volume of all ship's enclosed
spaces (from keel to funnel)
measured to the outside of the hull
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.
It represents the volume of the ship available
for transporting freight or passengers.
Displacement : it is the unit for the
total weight of the ship and her
contents, equivalent to the weight of
water displaced under any particular
condition of loading given in terms of
the defined weight system i.e metric
or long tons
The Panama Canal/Universal Measurement System
(PC/UMS) is based on net tonnage, modified for Panama
Canal purposes. PC/UMS is based on a mathematical
formula to calculate a vessel's total volume; a PC/UMS
net ton is equivalent to 100 cubic feet of capacity.
The Suez Canal Net Tonnage (SCNT) is derived with a
number of modifications from the former net register
tonnage of the Moorsom System and was established by
the International Commission of Constantinople in its
Protocol of 18 December 1873. It is still in use, as
amended by the Rules of Navigation of the Suez Canal
Authority, and is registered in the Suez Canal Tonnage
Thames measurement tonnage is another volumetric
system, generally used for small vessels such as yachts; it
uses a formula based on the vessel's length and beam.
Bunker is simply the name given
to the Fuel that is used to
Bunker fuel is technically any
type of fuel oil used aboard
ships. It gets its name from the
containers on ships and in ports
that it is stored in; in the days of
steam they were coal bunkers
but now they are bunker fuel
The Australian Customs and the
Australian Tax Office define a
bunker fuel as the fuel that
powers the engine of a ship or
Bunkering Ship =>
Bunker oil is literally the bottom of the barrel; the only
things more dense than bunker fuel are carbon
black feedstock and bituminous residue.
In the context of shipping, the labeling of bunkers as
previously described is rarely used in modern practice.
capacity(DWCC) or net capacity
is a measure of the deadweight
of a ship in terms of the cargo
she can transport, excluding
fuel, water, crew and everything
else that is not part of the ship.
DWCC- it is the most important
for the Charterers i.e whose
cargo has to be shipped. it gives
the weight of the cargo that the
vessel can carry.
The more fuel the vessel needs
the lower the DWCC. this also
depends on the water
water(salt, brackish) in summer
vessels have high DWCC
Dead weight all told(DWAT) is a term that states
the total amount of weight that a ship may carry
before it passes the waterline, including the weight
of: cargo, water, crew, fuel, food and anything else
that is not part of the ship and is not counted in its'
(Dead weight all told) = (Loaded displacement)(light displacement)
It is the line where the
hull of a ship meets the
surface of the water in
concept or reality.
It is also used as the
to keep a watch on the
It indicates the draft of
Also known as lighterage
Lightering is the process of
between vessels of
different sizes, usually
between a barge and
a bulker or oil tanker.
Lightering is undertaken to
reduce a vessel's draft in
order to enter port
facilities which cannot
accept very large ocean
The primary role of a
stevedore is the loading
and unloading of freight on
an off ships while they are
includes 1-mooring and unmooring
2- cleaning and preparing
3-stacking and securing
associated with the
transfer of cargo
as a dock worker, docker
or dock laborer, wharfie)
is usually the entry point
for individuals seeking a
carrier on the docks or
Stevedores can than
progress to became a
operator, foreperson or