Work out gross register tonnage instantly with clear inputs, formula shown and shareable results.
Under the 1969 Tonnage Convention gross tonnage is a dimensionless measure of total enclosed volume, GT = K1 x V with K1 = 0.2 + 0.02 log10(V). Net tonnage applies a similar coefficient to cargo spaces only and is floored at 30% of gross tonnage. Both drive port dues, manning and survey requirements.
Tonnage
GT = (0.2 + 0.02 log10 V) x V; NT from cargo volume, minimum 0.30 x GT
Marine results are planning estimates only. Verify against the vessel's approved stability booklet, loading manual, class society rules and applicable maritime regulations before loading or sailing.
No, despite the name. Gross and net tonnage are volume-based dimensionless numbers; displacement and deadweight are the mass measures.
Port dues, canal tolls, pilotage, registration fees and many regulatory thresholds are all assessed on gross or net tonnage.