What is Displacement?

The displacement of a ship (or any floating object) is defined as the number of tonnes of water it displaces.

It is usual to consider a ship displacing salt water of density 1.025 t/m3.However, fresh water values of displacement (1.000 t/m3) are often quoted in ship’s hydrostatic data.
& The volume of displacement is the underwater volume of a ship afloat i.e. the volume below the waterline.

To calculate the displacement (W) of a ship the following needs to be known:

  • The volume of displacement (V)
  • The density of the water in which it floats (r)

Since:            MASS = VOLUME X DENSITY

&The mass, or displacement, of a ship is calculated by: