Gigaton

The British tonne (ⁱ/tʌn/) (British and SI; SI symbol: t), which is the same as the metric ton in the United States, is a non-SI metric unit of mass equal to 1,000 kilograms; or one megagram (Mg); it is equivalent to approximately 2,204.6 pounds,1.10 short tons (US) or 0.984 long tons (imperial). Although not part of the SI per se, the tonne is "accepted for use with" SI units and prefixes by the International Committee for Weights and Measures, along with several other units like the bar, litre and day.

The SI symbol for the tonne is "t", adopted at the same time as the unit itself in 1879. Its use is also official, for the metric ton, within the United States, having been adopted by the US National Institute of Standards and Technology. It is a symbol, not an abbreviation, and should not be followed by a period. Informal and non-approved symbols or abbreviations include "T", "mT", "MT", and "mt". Some of these are SI symbols for other units: "T" is the SI symbol for the tesla and "Mt" is the SI symbol for megatonne (equivalent to one teragram); if describing TNT equivalent units of energy, this is equivalent to 4.184 petajoules.

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