Attotonne

The tonne (/tʌn/ ( listen)) (Non-SI unit, symbol: t), commonly referred to 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,1.102 short tons (US) or 0.984 long tons (imperial). Although not part of the SI, the tonne is accepted for use with SI units and prefixes by the International Committee for Weights and Measures.

The SI symbol for the tonne is "t", adopted at the same time as the unit in 1879. Its use is also official for the metric ton in the United States, having been adopted by the United States 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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