Convert Ton Register (ton reg) to Tun (tun) instantly.
About these units
Ton Register (ton reg)
A register ton, or ton register, is a unit of volume, not mass, equal to 100 cubic feet. It is used in maritime contexts to measure the internal capacity of ships—specifically cargo-carrying volume, not weight. Ship registries rely on register tons to calculate taxes, port fees, and cargo classifications. The unit dates back to 19th-century maritime law, where consistent volumetric measurement was critical for international shipping regulation. Despite changes in global trade and containerization, register tons remain important for historical vessel documentation, as well as for understanding older merchant and naval ship specifications.
Tun (tun)
A tun is a historical large cask unit commonly used in the wine and brewing industries, typically defined as 252 imperial gallons, or roughly 954 liters. It represented one of the largest standardized cask sizes in medieval and early modern Europe. Originally used for transporting wine, ale, and oil, the tun played an important role in commerce and maritime trade. Because taxes and tariffs were often levied per tun, its definition became central to economic regulation. The size also reflected the maximum volume that could be reliably transported in wooden casks without structural failure. Though obsolete today, the tun provides valuable insight into historical logistics, taxation, and the evolution of standardized container sizes in European trade networks.