A Vessel with a Panamax classification is one that can use the Panama Canal between the Atlantic and the Paciic Oceans. Vessels that are too big to fit through the locks on the canal are known as post-Panamax.
The maximum vessel size is determined by the locks which were installed when the 83 kilometre canal was completed in 1914 and will fit vessels up to 274 metres long and 32 metres wide.