Convert Electronvolt to Kilocalorie (eV → kcal)

Converting electronvolts to kilocalories 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 electronvolts

   Start with the number of electronvolts (eV) you want to convert.
2. 2
   Multiply by 3.829 × 10^-23

   The conversion factor from eV to kcal is 3.829 × 10^-23. Multiply your value by this number.
3. 3
   Read the result in kilocalories

   The result is your value in kilocalories (kcal).

Multiply the value in electronvolts by 3.829 × 10^-23. For the reverse direction, multiply by 2.611 × 10^22.

• ✓1 eV ≈ 1.602 × 10⁻¹⁹ J.
• ✓Particle physics scales: eV → keV → MeV → GeV → TeV (1000× each).
• ✓Photon energy (eV) × wavelength (nm) ≈ 1240.

• ✗Confusing eV with V (volt) — eV is energy, V is electric potential.
• ✗Mixing scales: treating MeV as twice eV — it's a million times larger.
• ✗Using eV for macroscopic energy — unwieldy numbers.

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

What is the Kilocalorie?

The kilocalorie equals 1,000 small calories or exactly 4.184 kilojoules and is the universal unit for measuring dietary energy in food. Confusingly, on US food labels and in popular usage, 'Calorie' (capital C) means kilocalorie — so a 200-Calorie cookie is actually 200,000 small calories, or 200 kcal. This convention dates to American chemist Wilbur Atwater's 19th-century nutrition research. Recommended daily intake is roughly 2,000 kcal for women and 2,500 kcal for men. The kilocalorie remains the everyday food-energy unit in the United States, while European labels show both kJ and kcal. Athletes track caloric burn during exercise in kcal: running burns about 100 kcal per mile. The kcal relates to the kilojoule (4.184 kJ = 1 kcal), the joule (1 kcal = 4,184 J), and the BTU (1 BTU ≈ 0.252 kcal). Marathon runners burn roughly 2,600 kcal during a 42-km race.

• Nutrition labels worldwide
• Diet and weight-management tracking
• Dietetics and clinical nutrition