Vessel & Tonnage

Load Line

The marks on a ship’s hull showing the maximum permitted loading draught for different water densities and seasons.

The load line (or Plimsoll line) is a set of marks amidships indicating the deepest a vessel may legally be loaded in different zones and seasons — tropical, summer, winter, and fresh versus salt water — to preserve adequate reserve buoyancy.

Load lines are regulated under the International Convention on Load Lines. Loading beyond the applicable mark is a serious safety and legal breach.

Also known as: plimsoll line, plimsoll mark, freeboard mark.

Related terms

Draught

The vertical distance from the waterline to the bottom of the keel — how deep the ship sits in the water.

Deadweight TonnageDWT

The total weight a ship can carry — cargo plus fuel, stores, crew and water — at her load line, in metric tonnes.

Plain-English reference definition — our own explanation of a standard shipping concept, not a licensed source or legal advice. See the full glossary or the broader maritime dictionary.

Last reviewed: June 2026.