TNT equivalent is a method of quantifying the energy released in explosions. The ton (or tonne) of TNT is a unit of energy equal to 4.184 gigajoules, which is approximately the amount of energy released in the detonation of one ton of TNT. The megaton is a unit of energy equal to 4.184 petajoules.

The kiloton and megaton of TNT have traditionally been used to rate the energy output, and hence destructive power, of nuclear weapons (see nuclear weapon yield). This unit is written into various nuclear weapon control treaties, and gives a sense of destructiveness as compared with ordinary explosives, like TNT. More recently, it has been used to describe the energy released in other highly destructive events, such as asteroid impacts. However, TNT is not the most energetic of conventional explosives. Dynamite, for example, has more than 60% more energy density (approximately 7.5 MJ/kg, compared to 4.6 MJ/kg for TNT).

Value

A gram of TNT releases 980–1100 calories upon explosion. To define the tonne of TNT, this was arbitrarily standardized by letting 1000 thermochemical calories = 1 gram TNT = 4184 J (exactly).

This definition is a conventional one. Explosives' energy is normally calculated using the thermodynamic work energy of detonation, which for TNT has been accurately measured at 1120 cal_th/g from large numbers of air blast experiments and theoretically calculated to be 1160 cal_th/g.

The measured pure heat output of a gram of TNT is only 651 thermochemical calories ≈ 2724 J, but this is not the important value for explosive blast effect calculations.

A kiloton of TNT can be visualized as a cube of TNT a bit under 10 meters on a side.

Grams TNT	Symbol	Tons TNT	Symbol	Energy
gram of TNT	g	microton of TNT	μt	4.184  J
kilogram of TNT	kg	milliton of TNT	mt	4.184  J
megagram of TNT	Mg	ton of TNT	t	4.184  J
gigagram of TNT	Gg	kiloton of TNT	kt	4.184  J
teragram of TNT	Tg	megaton of TNT	Mt	4.184  J
petagram of TNT	Pg	gigaton of TNT	Gt	4.184  J

Examples

• Conventional bunker buster bombs yield range from less than 1 ton to MOAB's 11 tonnes.
• Minor Scale, a 1985 United States conventional explosion utilizing of ANFO explosive to simulate a nuclear explosion, is believed to be the largest planned detonation of conventional explosives in history.
• The Little Boy atomic bomb dropped on Hiroshima on August 6, 1945, exploded with an energy of about . The nuclear weapons currently in the arsenal of the United States range in yield from to equivalent, for the B83 strategic bomb.
• During the Cold War, the United States developed hydrogen bombs with a maximum theoretical yield of ; the Soviet Union developed a prototype weapon, nick-named the Tsar Bomba, which was tested at , but had a maximum theoretical yield of . The actual destructive potential of such weapons can vary greatly depending on conditions, such as the altitude at which they are detonated, the nature of the target they are detonated against, and the physical features of the landscape where they are detonated.
• , when converted to kilowatt-hours, produces enough energy to power the average American household (in the year 2007) for 103,474 Years. For example, the estimated upper limit blast power of the Tunguska event could power the aforementioned home for just over 3,104,226 years. To put that in perspective: the blast energy could power the entire United States for 3.27 days.
• Megathrust earthquakes record huge M_W values, or total energy released. The 2004 Indian Ocean Earthquake released equivalent, but its M_E (surface rupture energy, or potential for damage) was far smaller at . The largest quake registered, the 1960 Chilean quake, released M_W almost 60 teratons or equivalent.
• On a much grander scale, supernova explosions give off about 10⁴⁴ joules of energy, which is about ten octillion (10²⁸) megatons of TNT.
• The maximum theoretical energy from total conversion of matter to energy when of antimatter annihilates with 1 kilogram of matter the reaction is 1.7975  J, which is equal to 42.96 Mt. This is given by the equation E = mc².

See also

• Relative effectiveness factor
• Nuclear arms race
• Ton
• Tonne

References

• Guide for the Use of the International System of Units (SI)
• Nuclear Weapons FAQ Part 1.3
• Rhodes, Richard. The Making of the Atomic Bomb, New York: Simon and Schuster, 1986.