Maritime Glossary
Gross Tonnage
Also known as: GT
A dimensionless measure of a ship's total enclosed volume, used as the basis for port dues, crew regulations, and convention applicability thresholds.
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Full Definition
Gross tonnage (GT) is calculated from total internal volume using GT = K₁ × V, where V is moulded volume and K₁ ranges from 0.2 to 0.32. It replaced gross register tonnage (GRT) under the Tonnage Convention 1969 (in force 1982). GT determines many regulatory thresholds: e.g., ISM Code applies to passenger ships ≥500 GT; MARPOL ORB requirements vary by GT; port tariffs and canal dues are based on GT. GT is not a weight measurement.
Domain Tags
vessel measurementsregulation