A gigaton (or gigatonne) is a Metric Unit of mass, equal to 1,000,000,000 (1 billion) Metric tons, 1,000,000,000,000 (1 trillion) kilograms, or 1 quadrillion grams. More commonly, though, the term gigaton is used to mean a gigaton of TNT

A gigaton of TNT is more commonly used as a measure of energy equal to that released by 1 billion metric tons of TNT. A gigaton is equal to 1,000 megatons, and is from the same family of terms. However, while megatons are commonly used as a measure of explosive devices, the most powerful explosive device ever constructed had a yield of only 58 megatons (October 30, 1961 - U.S.S.R.). Therefore the term gigaton is used mostly in seismology. An earthquake measuring an 8.0 on the richter scale releases approximately 1.01 gigatons of energy. Even in this context however, the term gigaton is not often used.

Although the gigaton unit does not appear to be in common enough usage to warrant an official abbreviation, Gt would be the logical choice.

See also

• megaton