Shipping Containers have revolutionized the transportation of non-bulk cargo around the world. Along with improvements in port handling facilities and intermodal transportation such as truck and rail, the container has made the world a smaller place. Today, goods manufactured in China can be on sale in your local Wal-Mart within a few weeks of leaving the factory in Guangzhou.

Containers are used by people around the world to move goods and used containers to store their inventory and even as portable offices and permanent housing. They come in two basic sizes, 20 feet long (6.1m) and 40 feet long (12.2m) are the two most often seen advertised as shipping containers for sale, although there are other lengths in use, mostly in various domestic markets. (48ft and 53ft are standard US domestic sizes) For trade between countries separated by half a world and a huge ocean or two, the TEU is the unit of measurement.

TEU stands for ‘Twenty Foot Equivalent Units’. It is equal to one standard 20 ft by 8 ft wide container. Height is not a factor and so you can have ‘High Cubes’ and ‘Half Height’ containers which are the same length and width but differ in height. The maximum gross mass for a 20 ft dry cargo container is 30,480kg, which includes the weight of the container so the actual payload mass is closer to 28,380kg.

A 40 ft container is a 2 TEU capacity container. Although twice the length of the 1 TEU 20 ft unit, it has a gross mass of 34,000kg and a payload mass of just 30,100kg. Doubling the length of the container wouldn’t double the payload unless the container itself was made a lot stronger and that would increase the TARE mass far beyond the capacity of a truck or rail car to carry it safely on roads and rail lines.

The width of railway tunnels and truck beds as well as the average clearance of bridges and overpasses are responsible for the height of both 20ft and 40ft units being kept at 8 ft (2.4m). Standardization of the container has facilitated trade between countries with differing gauges. The flatcars the container may travel on when offloaded from a ship and moved around in a new country are all the same, but the gauge of the wheels will differ. Many countries use a ‘standard gauge’ of 4ft 81/2in (1435mm) but Russia, India, Finland and Spain all use a ‘broader gauge’ and many countries in Africa and South America use a ‘narrower gauge’.