digplanet beta 1: Athena
Share digplanet:


Applied sciences






















The more heavily loaded a ship is, the lower it sits in the water. "Designated displacement" is a measurement the weight of water a ship displaces of when fully loaded and submerged to her load lines.[citation needed]

The displacement or displacement tonnage of a ship is the ship's weight. The name reflects the fact that it is measured indirectly, by first calculating the volume of water displaced by the ship, and then calculating the weight of that water. By Archimedes' principle, this is also the weight of the ship.

Displacement should not be confused with other measurements of volume or capacity typically used for commercial vessels such as net tonnage, gross tonnage, or deadweight tonnage.


Shipboard stability programs can be used to calculate a vessel's displacement

The process of determining a vessel's displacement begins with measuring its draft[1] This is accomplished by means of its "draft marks" (or "load lines"). A merchant vessel has three matching sets: one mark each on the port and starboard sides forward, midships, and astern.[1] These marks allow a ship's displacement to be determined to an accuracy of 0.5%.[1]

The draft observed at each set of marks is averaged to find a mean draft. The ship's hydrostatic tables show the corresponding volume displaced.[2]

To calculate the weight of the displaced water, it is necessary to know its density. Seawater (1025 kg/m³) is more dense than fresh water (1000 kg/m³);[3] so a ship will ride higher in salt water than in fresh. The density of water also varies with temperature.

Devices akin to slide rules have been available since the 1950s to aid in these calculations. It is done today with computers.[4]


Two similar destroyers berthed alongside each other. The one on the outboard is more heavily loaded and displaces more water.

There are terms for the displacement of a vessel under specified conditions:

Loaded displacement[edit]

  • Loaded displacement is the weight of the ship including cargo, passengers, fuel, water, stores, dunnage and such other items necessary for use on a voyage. These bring the ship down to its "load draft",[5] colloquially known as the "waterline".
  • Full load displacement and loaded displacement have almost identical definitions. Full load is defined as the displacement of a vessel when floating at its greatest allowable draft as established by classification societies (and designated by its "waterline").[6] Warships have arbitrary full load condition established.[6]
  • Deep load condition means full ammunition and stores, with most available fuel capacity used.[citation needed]

Light displacement[edit]

  • Light displacement (LDT) is defined as the weight of the ship excluding cargo, fuel, water, ballast, stores, passengers, crew, but with water in boilers to steaming level.[5]

Normal displacement[edit]

  • Normal displacement is the ship's displacement "with all outfit, and two-thirds supply of stores, ammunition, etc., on board."[7]

Standard displacement[edit]

  • Standard displacement, also known as "Washington displacement", is a specific term defined by the Washington Naval Treaty of 1922.[8] It is defined as the displacement of the ship complete, fully manned, engined, and equipped ready for sea, including all armament and ammunition, equipment, outfit, provisions and fresh water for crew, miscellaneous stores, and implements of every description that are intended to be carried in war, but without fuel or reserve boiler feed water on board.[8]


See also[edit]


  1. ^ a b c George, 2005. p.5.
  2. ^ George, 2005. p. 465.
  3. ^ Turpin and McEwen, 1980.
  4. ^ George, 2005. p. 262.
  5. ^ a b Military Sealift Command.
  6. ^ a b Department of the Navy, 1942.
  7. ^ United States Naval Institute, 1897. p 809.
  8. ^ a b Conference on the Limitation of Armament, 1922. Ch II, Part 4.


Original courtesy of Wikipedia: http://en.wikipedia.org/wiki/Displacement_(ship) — Please support Wikipedia.
This page uses Creative Commons Licensed content from Wikipedia. A portion of the proceeds from advertising on Digplanet goes to supporting Wikipedia.
106837 videos foundNext > 

Understanding Ship's Weight.

A guide for understanding Ship Weight. We all have studied about Lightweight, dead weight and displacement. When probed for an answer, we stumble as we ...

Displacement from Ship causing damage

Interesting from a scientific standpoint for sure. The displacement effect in the video is being caused by a 1000' long Freighter heading northbound on the St.

Why Do Ships Float?

Ever wonder why something as heavy as a cruise ship could float above the water? Learn about displacement with Jessi and The Giant Squid, ...

Ship Stability _ Effect of density on draft and displacement _Prob 6-10 Ex 5

Archimedes Principle - Class 9 Tutorial

Archimedes Principle states that the buoyant force on a submerged object is equal to the weight of the fluid that is displaced by the object. Through the video, we ...

Semi-Displacement ship vs. Displacement ship 3 ft/s to 10.5 ft/s

World's Largest Cruise Ship Sucks the Water off Fort Lauderdale Beach

Royal Caribbean's Oasis of the Seas departs Port Everglades, Florida. As the ship powers through the narrow inlet, it sucks the water out of the tidal areas ...

Displacement (ship)

The displacement or displacement tonnage of a ship is the ship's weight.The name reflects the fact that it is measured indirectly, by first calculating the volume of ...

time displacement ship & shield

here in movie Elysium are ships with time displacement and a man with a personal time displacement shield . must see!

Allure of the Seas and Oasis of the Seas - Weight, displacement and gross tonnage

Every now and then I see someone claiming that Oasis of the Seas, the biggest cruise ship in the world, weighs over 225000 tons. In this video I briefly explain ...

106837 videos foundNext > 

We're sorry, but there's no news about "Displacement (ship)" right now.


Oops, we seem to be having trouble contacting Twitter

Support Wikipedia

A portion of the proceeds from advertising on Digplanet goes to supporting Wikipedia. Please add your support for Wikipedia!

Searchlight Group

Digplanet also receives support from Searchlight Group. Visit Searchlight