TEU

From UG

TEU - The twenty-foot equivalent unit (often TEU or teu) is an inexact unit of cargo capacity often used to describe the capacity of container ships and container terminals.[1] It is based on the volume of a 20-foot long intermodal container, a standard-sized metal box which can be easily transferred between different modes of transportation, such as ships, trains and trucks.[1]

20 ft ~ 1 TEU
40 ft ~ 2 TEU 
....