How To Convert Electronvolt to Calorie
Formula: 1 electronvolt = 3.82929464e-20 calorie.
Example: Convert 2,500 electronvolt to calorie.
2,500 eV × 3.82929464e-20 = 9.57323660e-17 cal
To do it by hand, take the number of electronvolt you have. Multiply it by 3.82929464e-20. The result is in calorie. Because the number is very small, scientific notation is the easiest way to keep it accurate.
Quick Answer
1 Electronvolt = 3.82929464e-20 Calorie
- 10 eV = 3.82929464e-19 cal
- 1,000 eV = 3.82929464e-17 cal
- 1,000,000 eV = 3.82929464e-14 cal
Conversion Formula
cal = eV × 3.82929464e-20 Where: 3.82929464e-20 = (1.602176634e-19 J per eV) ÷ (4.184 J per cal)
This means an electronvolt is an extremely small amount of energy. We first express 1 eV in joules using the fixed elementary charge value. Then we change joules into calories using 1 cal = 4.184 J. Combining both steps gives one constant multiplier.
- Write your value in electronvolt (eV).
- Multiply by 3.82929464e-20.
- The result is the energy in calorie (cal).
Electronvolt
An electronvolt is a unit of energy equal to the energy gained by one electron when it moves through an electric potential difference of 1 volt. Symbol: eV.
It became common in early atomic and nuclear research because particle energies are conveniently sized in eV, keV, MeV, and GeV. Today it is used across physics, chemistry, and electronics.
- Describing photon energy in light and lasers.
- Comparing atomic and molecular energy levels.
- Stating particle energies in radiation and nuclear physics.
- Semiconductor band gaps in electronics.
- Plasma and space physics temperatures and energies.
Calorie
A calorie is a unit of energy often used for heat. In science, 1 calorie (cal) is commonly treated as 4.184 joules. Symbol: cal.
The calorie started as a heat unit used in early thermodynamics and chemistry. In food labels, “Calorie” usually means kilocalorie (kcal), which is 1,000 cal.
- Measuring small heat changes in chemistry.
- Older engineering and physics references for heat.
- Calorimetry experiments in labs and classrooms.
- Converting between joules and food energy units.
Is this Conversion of Electronvolt To Calorie Accurate?
Yes. This conversion is based on fixed and widely accepted standards. We use 1 eV = 1.602176634e-19 joule, which comes from the exact definition of the elementary charge in SI units. We then convert joules to calories using 1 cal = 4.184 J (the thermochemical calorie), a standard value used in many textbooks and lab calculations. Any tiny differences you may see elsewhere usually come from rounding or from using a different calorie definition. For more details about how we choose and verify constants, see our accuracy standards.
Real Life Examples
Electronvolt values often describe energy per particle, while calories often describe heat energy. Converting helps you compare tiny particle energies to familiar heat units.
- Red light photon (about 2 eV): 2 eV × 3.82929464e-20 = 7.65858928e-20 cal. This shows how tiny a single photon’s energy is in calorie units.
- Green light photon (about 2.5 eV): 2.5 eV × 3.82929464e-20 = 9.57323660e-20 cal. Still extremely small, even though it can be detected easily.
- Typical chemical bond energy scale (about 4 eV per bond): 4 eV × 3.82929464e-20 = 1.53171786e-19 cal per bond. Chemistry involves huge numbers of bonds, which is why bulk heat can be large.
- Semiconductor band gap (silicon about 1.12 eV): 1.12 eV × 3.82929464e-20 = 4.28881000e-20 cal. Engineers use eV because it fits semiconductor energy levels well.
- X-ray photon (10 keV = 10,000 eV): 10,000 eV × 3.82929464e-20 = 3.82929464e-16 cal. This helps compare radiation energies using common heat units.
- Gamma ray energy (1 MeV = 1,000,000 eV): 1,000,000 eV × 3.82929464e-20 = 3.82929464e-14 cal. Gamma rays are high energy per particle, but still tiny in calories.
- Electron accelerated by 500 volts (500 eV): 500 eV × 3.82929464e-20 = 1.91464732e-17 cal. Useful when estimating energies in vacuum tubes or detectors.
Quick Tips
- Use scientific notation, because calorie values per eV are extremely small.
- Fast method: multiply eV by 3.82929464, then move the decimal 20 places left.
- For keV, just add three zeros to eV first. 1 keV = 1,000 eV.
- For MeV, add six zeros. 1 MeV = 1,000,000 eV.
- If you already know joules, convert with cal = J ÷ 4.184.
- Keep enough significant digits if you are doing lab or research calculations.