Gross Register Ton to m³ Converter

About this calculator

Gross register tonnage (GRT) is a historical unit of ship volume — not weight — representing the total enclosed internal space of a vessel, where one register ton equals 100 cubic feet, or 2.8316846592 cubic meters. This calculator converts between GRT and cubic meters in either direction, letting you translate older ship documentation and registries into the metric volumes used in modern naval architecture and port paperwork.

GRT was the standard measure used for port fees, canal tolls, and registry classification for most of the 20th century before being formally superseded by the dimensionless Gross Tonnage (GT) system under the 1969 International Convention on Tonnage Measurement of Ships. Maritime historians, ship surveyors, and enthusiasts researching older vessels — many of which are still documented in GRT in historical records, insurance archives, and classic ship registries — rely on this conversion to compare old and new tonnage figures.