TNT Equivalent Calculator

TNT Equivalent Calculator finds the weight of TNT that matches an explosive from its heat of detonation, and converts joules, kWh or BTU to grams, tons or kilotons of TNT and back.

What the TNT Equivalent Calculator Works Out

The TNT Equivalent Calculator answers three linked questions. It tells you what weight of TNT matches a given weight of another explosive. It turns any amount of energy into a weight of TNT. It also runs the other way and gives the energy that a weight of TNT stands for.

The first job follows the heat of detonation method in the US Department of Defense manual UFC 3-340-02. The other two rest on a fixed unit of energy. The NIST conversion tables set one ton of TNT at 4.184 x 10⁹ joules, which is 4.184 MJ for every kilogram.

That fixed figure is why news reports can quote an asteroid strike, a volcano and a bomb test in the same unit. The energy of the event is worked out first, and then it is divided by 4.184 MJ/kg to give tons, kilotons or megatons of TNT.

TNT Equivalent Formula

For a real explosive, the TNT equivalent weight is its own weight scaled by a ratio of two heats of detonation. That ratio is called the TNT factor, and it is 1 for TNT itself.

$$W_{eq} = W_{exp} \times \frac{H_{exp}}{H_{TNT}}$$

• W_eq is the TNT equivalent weight, in the same unit as the weight you enter.
• W_exp is the weight of the explosive.
• H_exp is the heat of detonation of the explosive.
• H_TNT is the heat of detonation of TNT, set to 4.184 MJ/kg by default.

Take 6.5 kg of C4. The preset loads 4.715 MJ/kg for C4 against 4.184 MJ/kg for TNT, so the TNT factor is 4.715 / 4.184 = 1.127. Multiply by the weight and 6.5 kg of C4 comes out as 7.325 kg of TNT.

Both heats must be in the same unit, because only their ratio matters. If one field is in J/kg and the other in MJ/kg, the factor is wrong by a million, and the tool shows a warning when the factor falls outside the listed range.

The 12 presets in the TNT Equivalent Calculator come from the heat of detonation table in UFC 3-340-02, reprinted in the United Nations guideline IATG 01.80. The preset heats are that table’s ratios placed on the 4.184 MJ/kg scale, so C4 at 1.127 times TNT shows as 4.715 MJ/kg.

Joules in a Gram, Kilogram and Ton of TNT

The energy modes of the TNT Equivalent Calculator use one line of arithmetic. Energy equals the weight of TNT times 4.184 MJ/kg, and the weight of TNT equals the energy divided by the same number.

$$E = W_{TNT} \times 4.184 \ \text{MJ/kg}$$

So one gram of TNT is no more energy than a single food Calorie, and one kilogram is a little over one kilowatt-hour. What makes TNT powerful is the speed of release. The energy leaves in a tiny fraction of a second, where a heater would spread it over an hour.

Going the other way, 100 MJ of energy divided by 4.184 MJ/kg gives 23.9 kg of TNT. One joule on its own equals about 0.239 milligrams of TNT, or one newton of force moved through one meter.

The same step links this tool to the motion tools on the site. Find the energy of a moving object with the Kinetic Energy Calculator or the Impact Energy Calculator, then enter the joules here. A 3,000 J rifle shot from the Bullet Energy Calculator equals about 0.72 g of TNT.

Why C4 Shows 1.127 Here and 1.37 Elsewhere

Search results often list C4 at 1.37 times TNT, while the heat of detonation method gives 1.127. Both numbers are published. They answer different questions, and the basis has to be stated with the number.

The heat factor compares the chemical energy released per kilogram. The blast factors come from firing tests, where the pressure and impulse of the air blast are measured and matched to a TNT charge. NATO’s AASTP-1 lists those test values, and the UN guideline reprints them next to the heat-based ones.

The TNT Equivalent Calculator bases its headline result on the heat column, the same basis as the formula above. Its factor table shows all three columns for your weight, so 6.5 kg of C4 reads 7.325 kg of TNT by heat and 8.905 kg by blast pressure.

ANFO has no entry in the heat table, so its preset uses the blast factor of 0.82 and 6.5 kg of ANFO reads 5.33 kg of TNT. For any explosive outside the list, such as dynamite, pick Custom TNT factor and type a factor from your own source.

The 4.184 MJ/kg figure is a convention as well. It was chosen to equal exactly one kilocalorie per gram. Air blast tests on real TNT give about 4,686 J per gram, and published values run from 2,673 to 6,702 J per gram depending on how the charge is fired.

From Kilograms to Tons, Kilotons and Megatons

To convert kilograms to tons of TNT, divide by 1,000. Divide by 1,000 again for kilotons, and once more for megatons. A charge of 2,500 kg is 2.5 tons of TNT, or 0.0025 kilotons. The TNT Equivalent Calculator lists pounds, metric tons and kilotons together on one result card.

A ton of TNT in this system is a metric ton. One kiloton is 1,000 of those tons, and one megaton is a million. The Hiroshima bomb is put at about 15 kilotons and the Nagasaki bomb at about 20 kilotons. The largest device ever tested, the Soviet Tsar Bomba, reached about 50 megatons.

Natural events sit far above that. The 1980 eruption of Mount St. Helens is estimated at 24 megatons and the 1883 Krakatoa eruption at 200 megatons. The Chicxulub asteroid impact is estimated at 72 million megatons. In the energy modes, the tool shows how your figure compares with the nearest of these events.

TNT Equivalent Calculator Questions

What is TNT in chemistry, and is it made from gunpowder?

TNT is 2,4,6-trinitrotoluene, a single organic compound with the formula C₇H₅N₃O₆. It has nothing to do with gunpowder. Black powder is a loose mixture of potassium nitrate, charcoal and sulfur that burns fast, while TNT is one molecule that detonates. That steady, repeatable behavior is why TNT became the yardstick for every other explosive.

How heavy is TNT, and what does 3 tons of it look like?

The UN guideline lists TNT at a density of about 1.61 g/cm³, roughly 1.6 times as heavy as water. One kilogram fills about 620 cm³, a little over half a liter. Three metric tons take up about 1.86 cubic meters, which is a cube close to 1.23 m, or about 4 ft, on each side. A full kiloton would be a cube roughly 8.5 m on a side.

What is stronger than TNT: RDX, PETN or dynamite?

By heat of detonation, PETN is 1.17 times TNT, RDX and HMX are 1.15, and C4 is 1.13. Blast tests give RDX 1.14 and PETN 1.27 on peak pressure. Dynamite is not in either table, but nitroglycerin, its active ingredient, is 1.13 on the heat basis. Among the 12 presets of the TNT Equivalent Calculator, PETN has the highest factor and Baratol the lowest at 0.53.

What is the largest explosion ever measured in TNT terms?

The largest man-made explosion was the Tsar Bomba test of 1961, at about 50 megatons, which is over 3,000 times the 15 kiloton Hiroshima bomb. The Hiroshima bombing remains among the deadliest single explosions, with deaths estimated between 90,000 and 166,000. Among conventional accidents, the 1917 Halifax Explosion is put at about 2.9 kilotons.

How much TNT would it take to destroy a planet?

To pull Earth apart, you would have to supply its gravitational binding energy. For a uniform sphere that is three fifths of G times the mass squared over the radius, or about 2.24 x 10³² joules. Divided by 4.184 MJ/kg, the answer is roughly 5.4 x 10²² tons of TNT. That much TNT would weigh about nine times as much as Earth itself. The Energy to TNT Weight mode runs the same division for any energy you enter.

What is TNT used for today?

TNT is used as a military filling and in blasting, on its own and in blends. Current NATO and UN tables still list TNT mixtures such as Composition B, Cyclotol, Octol and Tritonal. Its other job is as a reference. Standard air blast formulas were built from TNT tests, so engineers convert any other explosive to a TNT weight before using them. More energy tools are listed on the Energy, Work and Power Calculators hub.