Electron Volt to Grams 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.

By convention, exactly 4,184 joules — the same as one thermochemical kilocalorie. Real TNT detonation yields vary by about ±2% depending on purity and confinement, but the defined value provides a fixed reference point. This makes the gram of TNT a convenient bridge between chemistry (calories) and explosive engineering.

TNT (trinitrotoluene) became the reference explosive because it is chemically stable, safe to handle, and was massively produced during both World Wars. Its consistent detonation properties made it a natural benchmark. Other explosives are rated by their "TNT equivalent" — for example, C-4 is about 1.34× TNT and ANFO is about 0.74× TNT.

A standard US consumer firecracker contains about 0.5–1 gram of TNT equivalent in flash powder. An M-80 (now illegal for consumer sale) contained roughly 3 g of TNT equivalent. Cherry bombs were about 1.5 g. Commercially sold fireworks are regulated by the CPSC to contain no more than 50 mg of flash powder per report charge.

A US M67 fragmentation grenade contains about 180 g of Composition B explosive, which has a TNT equivalence of about 1.33×, giving roughly 240 grams of TNT equivalent. The lethal radius is about 5 meters, with a casualty-producing radius of 15 meters. The fragmentation — not the blast energy alone — is the primary wounding mechanism.

One gram of TNT releases exactly 1 thermochemical kilocalorie (1 kcal = 4,184 J) by definition. This means a dietary Calorie (nutritional kcal) contains the same energy as detonating one gram of TNT. A 2,000-Calorie daily diet is energetically equivalent to 2 kg of TNT — though your body releases that energy over 24 hours, not in microseconds.