What is meant by the "tonnage" of a vessel?

The term "tonnage" refers to a measurement that indicates a vessel's size or its cargo-carrying capacity. This measurement helps determine how much weight or volume a ship can hold for transportation purposes. There are different types of tonnage calculations used in maritime practice, such as gross tonnage, which measures the overall size of the ship, and net tonnage, which reflects the volume of cargo the ship can carry after accounting for its own spaces like crew quarters and machinery.

Understanding tonnage is crucial for various reasons, including compliance with maritime regulations, determining port fees, and understanding cargo limits. Accurate tonnage information aids in ensuring that vessels are not overloaded, which can significantly impact safety and seaworthiness during voyages.