TNT equivalent


TNT equivalent is a convention for expressing energy, typically used to describe the energy released in an explosion. The is a unit of energy defined by that convention to be, which is the approximate energy released in the detonation of a metric ton of TNT. In other words, for each gram of TNT exploded, of energy is released.
This convention intends to compare the destructiveness of an event with that of traditional explosive materials, of which TNT is a typical example, although other conventional explosives such as dynamite contain more energy.

Kiloton and megaton

The "kiloton " is a unit of energy equal to 4.184 terajoules.
The "megaton " is a unit of energy equal to 4.184 petajoules.
The kiloton and megaton of TNT have traditionally been used to describe the energy output, and hence the destructive power, of a nuclear weapon. The TNT equivalent appears in various nuclear weapon control treaties, and has been used to characterize the energy released in such other highly destructive events as an asteroid impact.

Historical derivation of the value

Alternative values for TNT equivalency can be calculated according to which property is being compared and when in the two detonation processes the values are measured.
Where for example the comparison is by energy yield, an explosive's energy is normally expressed for chemical purposes as the thermodynamic work produced by its detonation. For TNT this has been accurately measured as 4686 J/g from a large sample of air blast experiments, and theoretically calculated to be 4853 J/g.
But, even on this basis, comparing the actual energy yields of a large nuclear device and an explosion of TNT can be slightly inaccurate. Small TNT explosions, especially in the open, don't tend to burn the carbon-particle and hydrocarbon products of the explosion. Gas-expansion and pressure-change effects tend to "freeze" the burn rapidly. A large open explosion of TNT may maintain fireball temperatures high enough so that some of those products do burn up with atmospheric oxygen.
Such differences can be substantial. For safety purposes a range as wide as has been stated for a gram of TNT upon explosion.
So, one can state that a nuclear bomb has a yield of 15 kt ; but an actual explosion of a pile of TNT may yield due to additional carbon/hydrocarbon oxidation not present with small open-air charges.
These complications have been sidestepped by convention. The energy liberated by one gram of TNT was arbitrarily defined as a matter of convention to be 4184 J, which is exactly one kilocalorie.
A kiloton of TNT can be visualized as a cube of TNT on a side.
Grams TNTSymbolTons TNTSymbolEnergy Energy Corresponding mass loss
gram of TNTgmicroton of TNTμt or 4.184 kilojoules1.162 Wh46.55 pg
kilogram of TNTkgmilliton of TNTmt or 4.184 megajoules1.162 kWh46.55 ng
megagram of TNTMgton of TNTt or 4.184 gigajoules1.162 MWh46.55 μg
gigagram of TNTGgkiloton of TNTkt or 4.184 terajoules1.162 GWh46.55 mg
teragram of TNTTgmegaton of TNTMt or 4.184 petajoules1.162 TWh46.55 g
petagram of TNTPggigaton of TNTGt or 4.184 exajoules1.162 PWh46.55 kg

Conversion to other units

1 ton TNT equivalent is approximately:

The relative effectiveness factor relates an explosive's demolition power to that of TNT, in units of the TNT equivalent/kg. The RE factor is the relative mass of TNT to which an explosive is equivalent: The greater the RE, the more powerful the explosive.
This enables engineers to determine the proper masses of different explosives when applying blasting formulas developed specifically for TNT. For example, if a timber-cutting formula calls for a charge of 1 kg of TNT, then based on octanitrocubane's RE factor of 2.38, it would take only 1.0/2.38 kg of it to do the same job. Using PETN, engineers would need 1.0/1.66 kg to obtain the same effects as 1 kg of TNT. With ANFO or ammonium nitrate, they would require 1.0/0.74 kg or 1.0/0.42 kg, respectively.
Calculating a single RE factor for an explosive is, however, impossible. It depends on the specific case or use. Given a pair of explosives, one can produce 2× the shockwave output but the difference in direct metal cutting ability may be 4× higher for one type of metal and 7× higher for another type of metal. The relative differences between two explosives with shaped charges will be even greater. The table below should be taken as an example and not as a precise source of data.
Explosive, gradeDensity
Detonation
vel. 		Relative
Effectiveness
Ammonium nitrate 0.8827000.42
Mercury fulminate4.4242500.51
Black powder 1.656000.55
Tanerit Simply 0.9027500.55
Hexamine dinitrate 1.3050700.60
Dinitrobenzene 1.5060250.60
HMTD 0.8845200.74
ANFO 0.9252700.74
TATP 1.1853000.80
Tovex Extra commercial product1.3356900.80
Hydromite 600 commercial product1.2455500.80
ANNMAL 1.1653600.87
Amatol 1.5062900.91
Nitroguanidine1.3267500.95
Trinitrotoluene 1.6069001.00
Hexanitrostilbene 1.7070801.05
Nitrourea1.4568601.05
Tritonal *1.7066501.05
Nickel hydrazine nitrate 1.7070001.05
Amatol 1.5565701.10
Nitrocellulose 1.4064001.10
Nitromethane 1.1363601.10
PBXW-126 *1.8064501.10
Diethylene glycol dinitrate 1.3866101.17
PBXIH-135 EB *1.8170601.17
PBXN-109 *1.6874501.17
Triaminotrinitrobenzene 1.8075501.17
Picric acid 1.7173501.17
Trinitrobenzene 1.6073001.20
Tetrytol 1.6073701.20
Dynamite, Nobel's 1.4872001.25
Tetryl1.7177701.25
Torpex *1.8074401.30
Composition B 1.7278401.33
Composition C-3 1.6076301.33
Composition C-4 1.5980401.37
Pentolite 1.6675201.33
Semtex 1A 1.5576701.35
Hexal *1.7976401.35
RISAL P *1.3959801.40
Hydrazine mononitrate1.5985001.42
Mixture: 24% nitrobenzene + 76% TNM1.4880601.50
Mixture: 30% nitrobenzene + 70% nitrogen tetroxide1.3982901.50
Nitroglycerin 1.5977001.54
Methyl nitrate 1.2179001.54
Octol 1.8386901.54
Nitrotriazolon 1.8781201.60
DADNE 1.7783301.60
Gelignite 1.6079701.60
Plastics Gel® 1.5179401.60
Composition A-5 1.6584701.60
Erythritol tetranitrate 1.7282061.60
Hexogen 1.7887001.60
PBXW-11 1.8187201.60
Penthrite 1.7784001.66
Ethylene glycol dinitrate 1.4983001.66
Trinitroazetidine 1.8586401.70
Octogen 1.8691001.70
Hexanitrohexaazaisowurtzitane 1.9793801.80
Hexanitrobenzene 1.9794001.85
MEDINA 1.6587001.93
DDF 1.98100001.95
Heptanitrocubane 1.929200N/A
Octanitrocubane 1.95106002.38

*: TBX or EBX, in a small, confined space, may have over twice the power of destruction. The total power of aluminized mixtures strictly depends on the condition of explosions.

Nuclear examples