<Li> 21.5 trillion kilocalories (≈ 21 Pcal) </Li> <Li> 85.2 trillion BTUs </Li> <P> or the energy released by combustion of the following: </P> <Dl> <Dd> <Ul> <Li> 21 500 kilotons of TNT - equivalent energy (≈ 21 Mt) </Li> <Li> 7009263000000000000 ♠ 2630000000 litres or 7008695000000000000 ♠ 695 000 000 US gallons of automotive gasoline </Li> </Ul> </Dd> </Dl>

Energy = mass x speed of light squared