Date of Award


Degree Type

Major Paper

Degree Name

Master of Arts in Marine Affairs


The tonnage measurement of ships is an important aspect of water-borne commerce. tonnage values are used to assess port fees, minimum manning requirements, and minimum safety equipment allowances aboard vessels. For example, as the tonnage value for a vessel goes up, so does the number of deckhands. Increasing the crew size may have other benefits. By adding more people to the vessel's crew complement there would be more people to ensure the vessel's safe transit. Therefore, changing tonnage values can have a direct impact on the safety of seagoing vessels. Since the creation of tonnage measurement as a means to determine a vessel's capacity, various measurement schemes have been created. Differences between measurement schemes in one country versus another have caused confusion in the application of shipping laws and regulations. The 1969 International Convention for the Tonnage Measurement of Ships seeks to unify the method by which all ships are measured and thus minimize the extent of interpretations currently practice. The most significant change is how the convention calculates two common tonnage measurement values; gross registered tonnage (GRT) and net registered tonnage (NRT). Gross registered tonnage is a value measurement of an entire vessel. Net registered tonnage is a volume measurement indicative of a vessel's earning capacity. The existing (domestic) U.S. tonnage measurement scheme measures only a few spaces, not the entire vessel. The convention eliminates many tonnage reducing mechanisms used by the United States. This paper discusses the history of tonnage, the existing U.S. measurement scheme and then focuses on implementing the Convention into U.S. law, particularly with respect to small vessels. Fully implementing the International Convention for the Tonnage Measurement of Ships as the United State's system of measurement will more than double the gross tonnage figures of U.S. vessels, yet with appropriate regulatory changes, have very positive effects on passenger, crew and vessel safety.