Twenty-foot equivalent unit

The standard intermodal container is long and wide. The height of such containers is most commonly but ranges from to . Another standard container is slightly more than twice as long: , dubbed a forty-foot equivalent unit (often FEU or feu). The reason the smaller container is short of 20 feet is to allow it to be stacked efficiently with 40-foot containers. The twistlocks on a ship are set so that two standard 20-foot containers have a gap of , allowing a single 40-foot container to fit precisely on top. The 40-foot containers have found wider acceptance, as they can be pulled by semi-trailer trucks. 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 40-foot container; in Europe and most other places a container of may be pulled as a trailer. Containers with a length of or are restricted to road and rail transport in North America. Although longer than 40 feet, these variants are put in the same class of forty-foot equivalent units. ==Equivalence==

The carrying capacity of a ship is usually measured by mass (the deadweight tonnage) or by volume (the net register tonnage). Deadweight tonnage is generally measured now in metric tons (tonnes). Register tons are measured in cu. ft, with one register ton equivalent to . As the TEU is an inexact unit, it cannot be converted precisely into other units. The related unit forty-foot equivalent unit, however, is defined as two TEU. It is common to designate a container as 2 TEU, rather than 2.25 TEU. The most common twenty-foot container occupies a space long, wide, and high, with an allowance externally for the corner castings; the internal volume is . However, both High cube and half height containers are also reckoned as 1 TEU. This gives a volume range of for one TEU. While the TEU is not itself a measure of mass, some conclusions can be drawn about the maximum mass that a TEU can represent. The maximum gross mass for a dry cargo container is . Subtracting the tare mass of the container itself, the maximum amount of cargo per TEU is reduced to about . Similarly, the maximum gross mass for a dry cargo container (including the High cube container) is . After correcting for tare weight, this gives a cargo capacity of . Twenty-foot "heavy tested" containers are available for heavy goods such as heavy machinery. These containers allow a maximum weight of , an empty weight of , and a net load of . ==See also==