Gross Register Tonnage (GRT)
Gross Register Tonnage (GRT) is a measurement of a ship’s internal volume, expressed in register tons, where one register ton equals 100 cubic feet. It represents the total enclosed space inside the vessel, including cargo holds, machinery rooms, crew areas, and other covered spaces. GRT was traditionally used to determine port fees, safety regulations, and vessel classification before newer systems like Gross Tonnage (GT) became standard. Even today, some ports and regulations still reference GRT for specific purposes.
GRT does not measure weight—it measures capacity. The larger the internal space, the higher the GRT. This measurement helps ports estimate how much space a vessel occupies in harbor facilities and determines fees such as docking, pilotage, and canal transit charges. Because GRT is tied to enclosed volume rather than cargo-carrying ability, it offers a clear, standardized way to assess ship size across different vessel types.
Understanding GRT is useful for operators working with older vessels or navigating regions where traditional tonnage systems remain in use. It also helps in evaluating vessel documentation, compliance requirements, and cost structures. While GT has replaced GRT internationally, both systems contribute to how ships are categorized and managed in maritime operations.
Frequently Asked Questions about Gross Register Tonnage (GRT)
Clear answers to the most common questions people have when learning about Gross Register Tonnage (GRT).
GRT measures internal volume using register tons (an older system), while GT uses a modern formula recognized globally. GT has now largely replaced GRT for regulatory use.
No. GRT measures total enclosed volume, not cargo capacity or weight. Cargo capacity depends on design, hold space, and vessel type.
Some ports, older vessels, and legacy regulations still reference GRT for fee calculations or documentation, so it remains relevant in certain maritime contexts.