Very often the energy released in large-scale events (e.g., earthquakes, meteor impacts, etc) is described in terms of some number of 'tons of TNT'. This may be all well and good for those with an intuitive sense of big explosions, but specifically, how many joules are there in the 'ton of TNT'? I can work out how many tons of water can be flashed to steam if you give me joules, but 'tons of TNT' means nothing in this regard, without a conversion factor. What is the conversion factor?
It is the energy released when TNT detonates - approximately 4.184 gigajoules per ton. Although TNT is under oxidized and can react further and so it releases about 2x more energy when it mixes with oxygen. But the bomb makers use 4.184 gigajoules per ton as the conversion factor.