Gross Tonnage (GT)

Gross Tonnage (GT) is a measurement of a ship’s overall internal volume. It is a dimensionless figure calculated based on the entire enclosed space of a vessel, including cargo spaces, crew accommodations, and machinery areas. Gross Tonnage is used to classify ships for regulatory purposes, port fees, and safety requirements.

Key Features:

 • Measurement Unit: Not a measure of weight but a dimensionless index derived from the ship’s total volume in cubic metres.

 • Scope: Includes all enclosed spaces on the vessel, such as cargo holds, engine rooms, and living quarters.

 • Formula: GT = K × V, where V is the volume in cubic metres of all enclosed spaces and K is a constant based on the ship’s geometry.

Applications:

 • Regulations: Determines compliance with international standards like SOLAS (Safety of Life at Sea) and MARPOL (pollution prevention).

 • Fees: Port dues and canal transit fees are often based on Gross Tonnage.