The basic concepts of ship length that we usually use include: Length over all (LOA, o/a, o.a. or oa), length beteen perpendiculars (p/p, p.p., pp, LPP, LBP or Length BPP), and tonnage length (registered length, load line length).

A: The total length refers to the horizontal distance between the front end of the bow and the rear end of the hull (including the bow and stern raised decks) and the superstructure (the ship with metal outer plates is measured to the inner surface, and the ship with non-metallic outer plates such as fiber reinforced plastic is measured to the outer surface), excluding the protrusions at the bow and stern (such as side decks, fenders, bulwarks, thrusters, outboard engines and their mounting brackets, false bows, false sterns, movable protrusions, etc.).

This length is mainly used when the ship enters the dock. In addition, the port berthing fee is generally charged according to the total length.

B: The length of the ship refers to the length measured between the perpendiculars at both ends of the summer load line. The length of a ship is often called the length between perpendiculars, and in some materials it is also called the length between two columns. The summer load waterline is usually used as the design full load waterline.

This length is the ship model used for manufacturing ship performance tests and the ship scale used for calculating the main navigation performance and loading capacity.

C: The tonnage length should be taken as 96% of the total length of the waterline at 85% of the minimum depth from the top of the keel plate, or the length from the front of the stem to the center of the rudder along the waterline, whichever is greater. For ships without rudders, it is taken as 96% of the total length of the waterline at 85% of the minimum depth.

This length is generally consistent with the load line length.