The tonne (SI unit symbol: t) is a metric system unit of mass equal to 1,000 kilograms (2,204.6 pounds). It is a non-SI unit accepted for use with SI. To avoid confusion with the ton, it is also known as the metric tonne and metric ton in the United States.
In SI units and prefixes, the tonne is a megagram (Mg), a rarely-used symbol, easily confused with mg, for milligram.
In the U.S., the National Institute of Standards and Technology supports the symbol "t" for the tonne. The abbreviation "mt" or "MT" is also used in the U.S.
Read more about Tonne: Symbol and Abbreviations, Origin and Spelling, Conversions, Derived Units, Alternative Usage