DEADWEIGHT TONNAGE OF A SHIP - Deadweight tonnage can be figured by taking the weight of a vessel which is not loaded with cargo and subtracting that figure from the weight of the vessel loaded to point where it is immersed to the maximum safe depth. This depth is noted with a marking on the ship's hull, the Plimsoll line. The safe depth varies by the time of year and water density and, in the case of DWT, the summer freeboard line is the measurement used. The displacement of water due to the load is measured in metric tons (tonnes or 1,000 kilograms).

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Deadweight Tonnage

The Meaning of Deadweight Tonnage of a Ship

by Paul Bruno 

Deadweight tonnage (DWT) refers to the carrying capacity of a vessel.

Deadweight tonnage can be figured by taking the weight of a vessel which is not loaded with cargo and subtracting that figure from the weight of the vessel loaded to point where it is immersed to the maximum safe depth.

This depth is noted with a marking on the ship's hull, the Plimsoll line.

The safe depth varies by the time of year and water density and, in the case of DWT, the summer freeboard line is the measurement used.

The displacement of water due to the load is measured in metric tons (tonnes or 1,000 kilograms).

The deadweight tonnage includes not only cargo, but also the weight of fuel, ballast, passengers and crew, and all of the provisions. It only excludes the weight of the ship itself.

Example

A vessel that weighs 2000 tons unloaded carries 500 tons crew and supplies. It can take on 500 tons of cargo in port, at which time it floats at the summer line of its Plimsoll line. The deadweight of this vessel would, therefore, be 1000 tons.

Deadweight Tonnage vs. Displacement Tonnage

Deadweight tonnage is distinct from displacement tonnage, which includes the weight of the ship as well as its carrying capacity.

Lightweight tonnage is the weight of the ship itself, including the hull, decking, and machinery, but not including ballast or any supplies that could be consumed, such as fuel and water (except for the liquids in the engine room systems).

Deadweight tonnage is the displacement tonnage minus the lightweight tonnage.

Paul Bruno

United States Coast Guard licensed Ship Master with Passenger Certification.

A marine contractor familiar with all ship systems who has worked in the industry for more than 20 years.

Has a USCG Master's License and a degree in Creative Nonfiction and Technical Writing, from the University of Wisconsin.

Experience

Paul Bruno is a former writer for ThoughtCo who contributed work for over five years on the maritime industry. He has worked with a variety of vessels throughout his maritime career, including various commercial ships as well as the Great Lakes schooner reproduction "Dennis Sullivan." As a marine contractor, Paul is familiar with all ship systems, and his lifelong passion for electronics has led to a focus on marine hardware and software development. When he is not working, Paul's favorite hobby is knot work, keeping busy with the nearly 4,000 documented knots, splices, and eyes.

Education

USCG Master's License, 1993

Creative Nonfiction and Technical Writing, University of Wisconsin, Milwaukee and University of Waikato, Hamilton NZ

Paul Bruno

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https://www.thoughtco.com/deadweight-tonnage-definition-2292971