Deadweight Tonnage (DWT): Meaning

Deadweight tonnage, written DWT, is the total weight a ship can carry when loaded to its maximum safe depth.

What DWT measures

DWT is the weight of everything a ship can carry: the cargo, the fuel, the fresh water, the ballast water, the stores and the crew. It is measured in metric tonnes, up to the deepest load line the ship is allowed to reach. A ship of 60,000 DWT does not carry 60,000 tonnes of cargo, because fuel and stores take part of it.

DWT and cargo intake

The cargo a ship can load on a voyage is its DWT minus the fuel for the voyage, the water, the stores and a small constant weight. The result changes with the length of the voyage and the density of the cargo. This is why a ship operator will often give the cargo intake for a given voyage when it makes an offer.

DWT, gross tonnage and displacement

Gross tonnage measures the closed volume of the ship, not its weight, and is used for fees and rules. Displacement is the weight of the water that the ship pushes aside, which equals the weight of the ship and everything on it. Lightship is the weight of the empty ship. DWT is the difference between the loaded displacement and the lightship.

DWT in chartering

Ships are grouped by DWT into size classes: Handysize, Supramax, Panamax and Capesize for dry cargo, and Aframax, Suezmax and VLCC for crude tankers. A charterer gives the cargo quantity, and the ship operator checks that its ship fits.

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