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Surprisingly the difference isn't quite as it seems. There's an important distinction between mass of the vessel's own structure, the bare necessities like fuel, stores & crew, and its payload. Naval engineering and insurance talks several interrelated measures, for our purposes "light load displacement" is the closest to the weight of the bare structure, while "full load displacement" includes all typical stores, fuel, crew, and payload. Conversely the linked measures "gross weight tonnage" is measure of volume rather than mass, and less relevant for this discussion. For combat vessels like USS Gerald Ford, most of the weight is in the structure itself, and while we don't have exact measures for the carrier, it's about 100,000 tonnes. For reference, an older generation but comparable carrier USS Nimitz has structure of 78280 tons ("light load displacement"), and all up weight 101196 tons ("full load displacement"). However for transport vessels like the linked Seawise Giant, the structure is small part of all up weight. While the ship plus cargo can go up to 646,642 long tons ("full load displacement"), the structure itself is much lighter: 81,879 long tons ("light load displacement"). Also the linked cruise ship, Icon of the Seas, has impressively high "gross weight tonnage" but again that's measure of volume. The displacement is a bit hard to find, people quote variously 100,000t or 120,000t without being specific light load or full load. So while the cruise ship is much larger by volume than the military vessel, the weight of the structure is closely comparable. The later is much more densely packed - keeping size down is a necessity for any combat craft, even the largest ones. |
Long ton = 2240 lb (1016 kg)
Short ton = 2000 lb (907 kg)
Tonne = 2205 lb (1000 kg)
Long tons are rarely used outside shipping. Short tons are what people mean when they say ton in America. Tonne is the metric ton and is what most of the rest of the world means when you hear something that sounds like ton.