Tonnage, a measure of a ship's cargo-carrying volumetric capacity, has historically formed the foundation of maritime commerce, taxation, and regulation. From medieval wine casks to modern standardized calculations, it reflects both practical requirements and evolving technical standards. Authors like Frank Coffee highlighted its role in determining port dues and freight claims, while Henry Bathurst Hanna explained net tonnage as the available space for passengers and cargo after subtracting operational areas.
E. Keble Chatterton outlined how gross tonnage encompasses all enclosed spaces, differentiating it from displacement measurements. The shift from traditional approaches—such as loading ships with tuns of wine—to the International Convention on Tonnage Measurement (1969) illustrates tonnage's transformation from an empirical estimate to a precise, universally regulated metric, ensuring uniformity in global shipping laws.