Displacement (ship)

Draft marks, by showing how low a ship is sitting in the water, make it possible to determine displacement.

The displacement or displacement tonnage of a ship is its weight. As the term indicates, it is measured indirectly, using Archimedes' principle, by first calculating the volume of water displaced by the ship, then converting that value into weight. Traditionally, various measurement rules have been in use, giving various measures in long tons.[1] Today, tonnes are more commonly used.

Ship displacement varies by a vessel's degree of load, from its empty weight as designed (known as "lightweight tonnage"[2]) to its maximum load. Numerous specific terms are used to describe varying levels of load and trim, detailed below.

Ship displacement should not be confused with measurements of volume or capacity typically used for commercial vessels and measured by tonnage: net tonnage and gross tonnage.

  1. ^ "Ship Tonnage Explained - Displacement, Deadweight, Etc". GG Archives. Retrieved 2019-01-14.
  2. ^ Dinsmore, Ben (16 May 2011). "A Guide to Understanding Ship Weight and Tonnage Measurements". The Maritime Site. Archived from the original on 29 May 2011. Retrieved 14 February 2018.{{cite web}}: CS1 maint: unfit URL (link)