Convert Calorie to Electronvolt (cal → eV)

Converting calories to electronvolts is straightforward: multiply by the conversion factor. Follow these three steps to do it by hand or in your head.

1. 1
   Take your value in calories

   Start with the number of calories (cal) you want to convert.
2. 2
   Multiply by 26,114,473,967,543,833,000

   The conversion factor from cal to eV is 26,114,473,967,543,833,000. Multiply your value by this number.
3. 3
   Read the result in electronvolts

   The result is your value in electronvolts (eV).

Multiply the value in calories by 26,114,473,967,543,833,000. For the reverse direction, multiply by 3.829 × 10^-20.

• ✓1 cal = 4.184 J. 1 kcal = 4184 J.
• ✓Scientific "calorie" and nutrition "Calorie" differ by 1000×.
• ✓Prefer joules in modern scientific writing.

• ✗Assuming "calories" on food labels means gram calories — they are kcal.
• ✗Mixing gram calories and kilocalories in calculations.
• ✗Confusing calorie (energy) with calorimeter (apparatus).

What is the Calorie?

The calorie equals exactly 4.184 joules (the 'thermochemical calorie') and is the historical unit for heat in chemistry and physics. It was originally defined as the heat needed to raise 1 gram of water by 1°C (a definition that varied slightly with starting temperature, hence multiple 'calories' — 4.184 J was set as the exact thermochemical convention). The calorie is widely used in older physics and chemistry literature for reaction energies, specific heat capacities, and thermodynamic calculations. Note: this 'small calorie' (lowercase c) is 1/1000 of the food Calorie (capital C) used in nutrition. The chemistry calorie relates to the joule (4.184 J = 1 cal), the kilocalorie (1,000 cal = 1 kcal = 1 food Calorie), and the BTU (1 BTU ≈ 252 cal). Modern SI usage in scientific publications has largely replaced the calorie with the joule, but it persists in medical and chemistry contexts.

• Thermodynamics and older physics texts
• Chemistry energy calculations
• Some engineering heat-transfer contexts

What is the Electronvolt?

The electronvolt equals approximately 1.602176634 × 10⁻¹⁹ joules (a tiny amount of energy) and is the standard unit in atomic physics, particle physics, and semiconductor electronics. Defined as the energy gained by an electron accelerated through a potential difference of 1 volt, the eV is the natural scale for atomic and molecular energies. The energy required to ionize a hydrogen atom is 13.6 eV, the band gap of silicon (relevant for transistors and solar cells) is 1.12 eV, and visible light photons carry 1.6–3.3 eV per photon. Particle physicists routinely use MeV (million eV), GeV (billion eV), and TeV (trillion eV): the Large Hadron Collider accelerates protons to 6.5 TeV. The eV relates to the joule (1 eV ≈ 1.602 × 10⁻¹⁹ J), the kilojoule per mole (96.485 kJ/mol per eV), and atomic mass units via E = mc². It is the universal energy unit in physics literature.

• Particle physics (TeV, GeV, MeV)
• Atomic and molecular physics
• Semiconductor band gaps