Ship size, side view

Length over all ( Loa) = Horizontal distance over the extremities between bow and stern

Length between perpendiculars ( Lbp) = distance from aft perpendicular ( centre of rudderstock) to forward perpendicular ( intersection of waterplane and bow at design draft)

Load line length ( Lll) = length as used in freeboard calculation

Beam ( breadth) ( B) = width of the hull usually measured inside shell plating ( moulded)

Depth ( H) = height from baseline to uppermost deck at side measured inside the plating

Draught ( T) = underwater depth of a vessel


It is the difference between the draught at stem ( forward) and the draught at the stern;

A vessel could be:


Moulded dimensions

Distance measured a tin side of the shell plating ( i. e. distance measured between 2 points excluding the plate thickness)

Base Line

Measured imaginary horizontal lenght of the upper part of the spine plate.

Deck Line

Horizontal line marked usually at the top of the main deck/ free board deck at the ship’ s side

Load Line

Waterline of a vessel immersed in water:

Air draught

Vertical distance between the water line and the highest point of the vessel

Freeboard Mark

Shows the maximum allowed value of a sinking ship, leaving enough space for safety. Lloyd’ s Register of British and Foreign Shipping was the first to introduce loading recommendations in 1835.

In 1860 Samuel Plimsoll ( 10 February 1824 – 3 June 1898) , a British politician, took up the load line cause after more and more vessels were lost due to overloading. His efforts against what was called at the time “ coffin ships” ( unseaworthy, overloaded vessels, often heavily insured, in which owners risked the lives of their crew) were paid off when in 1876 the United Kingdom

Merchant Shipping act  has mandated the marking load line. The location of the loading line mark is not connected to the 1894 law.
In the 1930 Load Line Convention, the application of load line regulations became international. Later on, in 1966 during the Load Line Convention held in London, the rules of 1930 were re- examined and amended.