Twenty-foot equivalent units

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. It is based on the volume of a 20-foot-long (6.1 m) intermodal container, a standard-sized metal box which can be easily transferred between different modes of transportation, such as ships, trains and trucks.

The container is defined by its length though there is a lack of standardisation in regard to height, ranging between 4 feet 3 inches (1.30 m) and 9 feet 6 inches (2.90 m), with the most common height being 8 feet 6 inches (2.59 m). Also, it is common to designate 45-foot (13.7 m) containers as 2 TEU, rather than 2.25 TEU.

The standard intermodal container is designated as twenty feet long and 8 feet (2.44 m) wide. Additionally there is a standard container with the same width but a doubled length of forty feet called a 40-foot container, which equals one forty-foot equivalent unit (often FEU or feu) in cargo transportation (considered to be two TEU, see below).

In order to allow stacking of these types a forty-foot intermodal container has an exact length of 40 feet (12.192 m), while the standard twenty-foot intermodal container is slightly shorter having an exact length of 19 feet 10.5 inches (6.058 m). The twistlocks on a ship are put at a distance so that two standard twenty-foot containers have a gap of three inches which allows a single forty-foot container to be put on top.

The forty-foot containers have found wider acceptance, as they can be pulled by semi-trailer truck. The length of such a combination is within the limits of national road regulations in many countries, requiring no special permission. As some road regulations allow longer trucks, there are also variations of the standard forty-foot container — in Europe and most other places a container of 45 feet (13.72 m) may be pulled as a trailer. Containers with a length of 48 feet (14.63 m) or 53 feet (16.15 m) are restricted to road transport in the United States. Although longer than 40 feet, these variants are put in the same class of forty-foot equivalent units.

Container ships only take 40-foot and 20-foot containers below deck, plus 45-foot containers above deck. Ninety percent of the containers that container ships carry are 40-foot units. As container ships carry 90% of the world's freight, at least 81% of the world's freight moves via 40-foot containers.

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