Maritime glossary · Gross Tonnage
GT
A unitless measure of a vessel’s total enclosed volume — used for port dues, pilotage fees, and SOLAS thresholds.
Definition
Gross Tonnage is a function of the ship’s total enclosed volume, calculated under the 1969 International Convention on Tonnage Measurement of Ships. Despite the name, GT is not a weight — it is a logarithmic volume figure. GT thresholds drive a lot of maritime regulation: vessels above 500 GT must carry an ISM Code certificate, vessels above 300 GT must broadcast AIS, and pilotage and port dues are usually tariffed against GT.
Worked example
A 50,000 DWT bulker has a GT around 30,000. A 23,000 TEU ultra-large container ship has a GT around 235,000.
How Vessel Hunter uses GT
Every vessel record in Vessel Hunter carries GT alongside DWT, so commercial teams can sanity-check the size profile and compliance teams can confirm which regulations apply.
Related terms
- NTNet Tonnage
Gross Tonnage minus the volume of spaces not available for cargo — used for canal tolls and certain port dues.
- DWTDeadweight Tonnage
The maximum weight in tonnes a vessel can carry — cargo, fuel, ballast, crew, stores — without exceeding its load line.
- ISM CodeInternational Safety Management Code
The mandatory IMO framework for safe management and operation of ships — basis of the Document of Compliance and the Safety Management Certificate.
- AISAutomatic Identification System
The VHF radio system every commercial vessel uses to broadcast its position, course, and identity.
The bigger picture
GT is one piece of the commercial maritime picture Vessel Hunter pulls together for shipyards, port agents, and service providers. Every vessel record bundles AIS, ownership, inspections, dry-dock history, casualty record, classification status, and a verified contact for the operator decision-maker behind the ship, so the team that reaches out first wins the work.
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