Freight Space refers to all the spaces within a ship where cargo can be loaded. Freight capacity refers to the production capacity of the transport service provided by the ship. Therefore, it refers not only to the amount of physical space inside the ship but also to the space inside the ship that is equipped with equipment and where crew members are onboard. However, in reality, the speed of ships and their routes vary, so the freight capacity in shipping statistics is represented by the total tonnage of ships currently in operation.
Source : National Logistics Information Center of Korea