Electron Volt to Kilograms of TNT

Because subatomic energies in joules have absurdly small exponents — a visible-light photon carries about 3 × 10⁻¹⁹ J, but a convenient 1.9 eV. The electron volt is scaled to the quantum world, making numbers human-readable. It also doubles as a mass unit (via E = mc²): a proton is 938.3 MeV/c², far easier to work with than 1.673 × 10⁻²⁷ kg.

Visible light photons range from about 1.65 eV (deep red, 750 nm) to 3.1 eV (violet, 400 nm). Green light, where the human eye is most sensitive, sits around 2.3 eV. Ultraviolet photons start at 3.1 eV and can exceed 100 eV in the extreme UV. These energies are why UV can damage DNA (breaking molecular bonds of 3–5 eV) while visible light cannot.

A semiconductor's bandgap — the minimum energy to free an electron from its bond — is expressed in eV. Silicon has a bandgap of 1.12 eV, gallium arsenide 1.42 eV, and gallium nitride 3.4 eV. The bandgap determines which wavelengths of light a solar cell can absorb and what color an LED emits. Lower bandgap means longer-wavelength (redder) light.

The LHC accelerates protons to 6.5 TeV (6.5 × 10¹² eV) per beam, giving collisions a center-of-mass energy of 13 TeV. That sounds enormous, but 13 TeV is only about 2 microjoules — the kinetic energy of a flying mosquito. The power of the LHC lies in concentrating that energy into a space a million times smaller than an atom.

Multiply by 1.602 176 634 × 10⁻¹⁹. So 1 eV = 1.602 × 10⁻¹⁹ J, 1 keV = 1.602 × 10⁻¹⁶ J, and 1 MeV = 1.602 × 10⁻¹³ J. This conversion factor is exactly the elementary charge in coulombs, because an electron volt is defined as the energy gained by one electron charge crossing one volt of potential.

One kilogram of TNT releases 4.184 MJ — enough to shatter windows within several meters and cause serious injury at close range. In open air, 1 kg of TNT produces a blast overpressure lethal to humans within about 2–3 meters. The effect depends heavily on confinement: the same charge inside a vehicle or building is far more destructive than in open ground.

One kilogram of TNT (4.184 MJ) is roughly the kinetic energy of a 1,500 kg car traveling at 75 km/h, or the energy stored in about 120 mL (half a cup) of petrol. It is also the chemical energy in roughly one large meal (1,000 kcal). The difference is that TNT releases its energy in microseconds rather than hours.

Mining engineers express blast charge sizes in kg of TNT equivalent to standardize across different commercial explosives. A typical quarry blast hole uses 5–50 kg of ANFO (ammonium nitrate/fuel oil), equivalent to roughly 4–37 kg TNT. Building demolition charges range from 10 to several hundred kg TNT equivalent, carefully placed at structural weak points.

A standard 155 mm artillery shell contains about 7–11 kg of TNT equivalent. A 500 lb (Mk 82) air-dropped bomb holds roughly 87 kg of TNT equivalent. An RPG-7 warhead is about 1–2 kg TNT equivalent. Anti-tank mines range from 5–10 kg TNT equivalent. These figures represent explosive fill, not total weapon weight.

A standard stick of commercial dynamite (about 200 g, 20 cm long) has a TNT equivalence of roughly 0.25–0.30 kg, since dynamite is about 1.25–1.5× as powerful as TNT by weight. Eight sticks of dynamite are roughly equivalent to one kilogram of TNT. Modern mining rarely uses traditional dynamite, preferring cheaper ANFO or emulsion explosives.