Megatonne

Symbol and abbreviations

The BIPM 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 (NIST). It is a symbol, not an abbreviation, and should not be followed by a period. Use of lower case is significant, and use of other letter combinations can lead to ambiguity. For example, T, MT, mT, are the SI symbols for the tesla, megatesla, and millitesla, respectively, while Mt and mt are SI-compatible symbols for the megatonne (one teragram) and millitonne (one kilogram). If describing TNT equivalent units of energy, one megatonne of TNT is equivalent to approximately 4.184 petajoules.