In the UK, short tons are rarely used. The word ton is taken to refer to a long ton, and metric tons are distinguished by the tonne spelling. Most Commonwealth countries followed British practice with the exception of Canada, which used short tons in preference to long tons, as in the United States.
United States 
In the United States it is often called simply ton without distinguishing it from the tonne (1,000 kilograms or 2,204.62262 pounds) or the long ton (2,240 pounds or 1,016.0469088 kilograms); rather, the other two are specifically noted. There are, however, some U.S. applications for which unspecified tons normally means long tons (for example, Navy ships) or metric tons (world grain production figures).
Both the long and short ton are defined as 20 hundredweights, but a hundredweight is 100.000000 pounds (45.359237 kg) in the U.S. system (short or net hundredweight) and 112 pounds (50.80234544 kg) in the imperial system (long or gross hundredweight).
See also 
- Long ton, 2,240 lb (1,016.0469088 kg).
- Tonne, also known as a metric ton (t), equal to 1,000 kg (2,204.6226218 lb) or 1 megagram.
- Tonnage, volume measurement used in maritime shipping, originally based on 100 cubic feet (2.8316846592 m3).
- "NIST Handbook 44 Specifications: Handbook 44 – 2013 Appendix C – General Tables of Units of Measurement". April 26, 2006. p. C-6. Retrieved October 13, 2008. "20 hundredweights = 1 ton"
- "Naval Architecture for All". United States Bureau of Transportation Statistics. Retrieved October 13, 2008.