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Nautical Measurements

Deadweight Tonnage is a ship's actual carrying capacity measured in long tons. (A long ton equals 2,240 pounds, 1,016 kilograms, or 1.016 metric tons). Deadweight tonnage includes cargo, crew, passengers, fuel, supplies, and spare parts. Freighters and tankers are generally described in terms of deadweight tonnage.

Displacement Tonnage is the number of long tons of water displaced (occupied) by a ship. This measurement is generally used for naval craft.

Gross Tonnage is the amount of a ship's enclosed space. It is a measure of volume, not weight, and is expressed in units of 100 cubic feet (2.8 cubic meters). A ship of 5,000 gross tons has 500,000 cubic feet (14,158 cubic meters) of enclosed space. Passenger ships are usually measured in terms of gross tonnage.

Knot means one nautical mile per hour. A ship's speed is measured in knots. A nautical mile equals 6,076 feet (1,852 meters), and a land mile equals 5,280 feet (1,609 meters). Therefore, a ship that does 10 knots travels somewhat faster than 10 miles (16 kilometers) per hour.

Net Tonnage is the amount of revenue-producing space of a ship. A ship's net tonnage is found by subtracting the engine room, crew's quarters, and all other areas that do not hold cargo from the gross tonnage. Net tonnage is used to determine harbor fees, taxes, and canal tolls.

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The Robinson Library >> Naval Science

This page was last updated on 08/08/2017.