TNT Equivalent Calculator
This TNT equivalent calculator helps you find the TNT equivalent weight for different explosives. Using this calculator, you can find answers to questions like: how many kilograms of C4 produce energy equivalent to 1 kg of TNT?
There was a need to adopt a universal quantity to compare the energy output of various explosives. TNT (trinitrotoluene) equivalent weight was chosen because its blast characteristics resemble most solid-type explosives. Blast characteristics data is crucial to design protective structures, and the TNT equivalent weight helps determine the pressure loads acting on structures during an explosion event. In addition to this, it is also used as a unit of energy conversion.
TNT Equivalence
TNT equivalence is a function of the ratio of heat produced during detonation. One kilogram of TNT produces 4.184 MJ of energy (1,800 BTU/lb). For an explosive having a heat of detonation Hexp, the TNT equivalent weight Weq is:
Weq = Wexp × (Hexp / HTNT)
where the heat of detonation is expressed in MJ/kg and weight is in kg. The ratio of heat of detonation is called the TNT factor.
How to Calculate TNT Equivalent
- Select the unit system — Metric (kg, MJ/kg) or Imperial/American (lb, BTU/lb).
- Choose an explosive type from the preset dropdown — the heat of detonation will be filled automatically — or enter a custom value.
- Enter the weight of the explosive in kilograms (or pounds for Imperial).
- Click Calculate. The calculator returns the TNT factor and TNT equivalent weight in both metric and imperial units, along with the total energy released.
Common Explosives — Heat of Detonation
| Explosive | Heat of Detonation (MJ/kg) | BTU/lb | TNT Factor |
|---|---|---|---|
| TNT | 4.184 | 1,800 | 1.000 |
| Torpex / Tetrytol 75/25 | 5.021 | 2,160 | 1.200 |
| PETN | 4.906 | 2,111 | 1.173 |
| HMX / RDX | 4.821 | 2,074 | 1.152 |
| C4 / NG (Nitroglycerin) | 4.715 | 2,029 | 1.127 |
| Amatol 80/20 | 4.895 | 2,107 | 1.170 |
| PBX 9407 | 4.757 | 2,047 | 1.137 |
| Pentolit 50/50 | 4.545 | 1,955 | 1.086 |
| Comp B | 4.566 | 1,965 | 1.091 |
| Tetryl | 4.481 | 1,928 | 1.071 |
| HBX-3 | 4.268 | 1,836 | 1.020 |
| Ammonium Picrate | 4.058 | 1,746 | 0.970 |
| Tritonal | 3.891 | 1,674 | 0.930 |
| NQ (Nitroguanidine) | 3.165 | 1,362 | 0.756 |
| ANFO | 3.682 | 1,584 | 0.880 |
| Baratole | 2.209 | 950 | 0.528 |
| Ammonium Nitrate | 1.757 | 756 | 0.420 |
| Natural Gas | 0.669 | 288 | 0.160 |
FAQs
What is the TNT factor?
The TNT factor is the ratio of the heat of detonation of an explosive to the heat of detonation of TNT (4.184 MJ/kg). A factor greater than 1 means the explosive releases more energy per kilogram than TNT; a factor less than 1 means it releases less energy.
How many kg of C4 equals 1 kg of TNT?
C4 has a heat of detonation of 4.715 MJ/kg, giving it a TNT factor of approximately 1.127. This means 0.888 kg of C4 produces the same energy as 1 kg of TNT.
What is the difference between metric and imperial units?
In the metric system, the heat of detonation is expressed in MJ/kg and weight in kilograms. In the American (imperial) system, the heat of detonation is expressed in BTU/lb and weight in pounds. The conversion is: 1 MJ/kg = 430.20 BTU/lb.
Why is only one-third of the energy released in the detonation blast?
Only about one-third of the chemical energy is released upon detonation. The rest is released at a slower rate as the explosive products burn and react with the surrounding air — which is a function of heat of combustion, not detonation.
What is TNT equivalent used for?
TNT equivalent is used in structural engineering to design blast-resistant structures, in mining and demolition for safety calculations, in seismology to compare the energy of earthquakes, and as a standard unit of energy comparison across different explosives and energy events.