What measurement is used to determine the weight of a ship?

Displacement in tons is the most accurate measurement used to determine the weight of a ship. It refers to the total weight of water that the ship displaces when it is floating, which correlates directly to the ship's weight. As the ship is submerged, the volume of displaced water equates to the weight of the vessel itself, expressed in tons.

While gross tonnage, net tonnage, and deadweight tonnage are also commonly used measurements in maritime contexts, they serve different purposes. Gross tonnage is a measure of the overall internal volume of a ship, including all spaces such as cargo holds and living quarters. Net tonnage accounts for the volume that is available for carrying cargo, excluding spaces used for machinery and crew. Deadweight tonnage measures the total weight a ship can safely carry, including cargo, fuel, and provisions but does not reflect the ship's actual weight.