Megaelectronvolts to joules (MeV to J) converter

What is a megaelectronvolts to joules converter?

A megaelectronvolts to joules converter is an online tool that translates an energy quantity written in megaelectronvolts (MeV) into the equivalent number of joules (J), and the other way around. The megaelectronvolt belongs to the world of particle and nuclear physics, where energies are tiny on the everyday scale, while the joule is the SI unit used for energy throughout science and engineering. Because the two units differ by more than a dozen orders of magnitude, doing the arithmetic by hand is error-prone, so a dedicated converter keeps the exponents straight for you.

One electronvolt (eV) is the kinetic energy gained by a single electron when it is accelerated through a potential difference of one volt. A megaelectronvolt is simply one million electronvolts. Typical nuclear binding energies, gamma-ray photon energies, and the rest energies of light particles are most naturally expressed in MeV, which is why the unit is so common in physics literature.

How it works

The conversion rests on a single fixed constant. Since the 2019 redefinition of the SI base units, the elementary charge is defined exactly, which makes the electronvolt an exact quantity:

• 1 eV = 1.602176634 × 10⁻¹⁹ J (exact)
• 1 MeV = 10⁶ eV = 1.602176634 × 10⁻¹³ J

To go from megaelectronvolts to joules you multiply by 1.602176634 × 10⁻¹³. To go from joules back to megaelectronvolts you divide by the same number (equivalently, multiply by about 6.241509074 × 10¹²). The converter also lets you read the result in kilojoules (kJ), megajoules (MJ), or thermochemical calories (cal), where 1 cal = 4.184 J.

Formula

$E_{\text{J}} = E_{\text{MeV}} \times 1.602176634 \times 10^{-13}$

$E_{\text{MeV}} = E_{\text{J}} \div 1.602176634 \times 10^{-13} = E_{\text{J}} \times 6.241509074 \times 10^{12}$

Conversion table

The table below lists common megaelectronvolt values alongside their exact joule equivalents.

Examples

Example 1: One megaelectronvolt to joules

Convert 1 MeV to joules using the conversion factor:

$1 \text{ MeV} \times 1.602176634 \times 10^{-13} = 1.602176634 \times 10^{-13} \text{ J}$

This is the energy carried by, for example, a 1 MeV gamma-ray photon.

Example 2: One joule to megaelectronvolts

A single everyday joule is an enormous amount of energy on the particle scale. Dividing by the conversion factor gives:

$1 \text{ J} \times 6.241509074 \times 10^{12} = 6.241509074 \times 10^{12} \text{ MeV}$

That is roughly 6.24 trillion megaelectronvolts packed into one joule.

Example 3: One megaelectronvolt in calories

The joule field can also display the result in thermochemical calories (1 cal = 4.184 J):

$\frac{1.602176634 \times 10^{-13} \text{ J}}{4.184 \text{ J/cal}} \approx 3.829293 \times 10^{-14} \text{ cal}$

Example 4: One million megaelectronvolts to joules

Scaling up to 1 000 000 MeV (1 TeV):

$1{,}000{,}000 \text{ MeV} \times 1.602176634 \times 10^{-13} = 1.602176634 \times 10^{-7} \text{ J}$

Even a teraelectronvolt of energy is still well under a millionth of a joule.

Notes

• The conversion factor is exact because the elementary charge has been fixed by definition since the 2019 SI revision, so no rounding uncertainty is introduced by the unit change itself.
• 1 MeV equals one million electronvolts; if you are working with single electronvolts instead, divide your MeV figure by 1 000 000 first.
• The joule output can be shown in joules, kilojoules, megajoules, or calories. Watch the exponents when reading very small joule values.
• Calorie results use the thermochemical calorie (4.184 J), not the “large” food Calorie (kilocalorie).

Frequently asked questions

How many joules are in one megaelectronvolt?

One megaelectronvolt equals 1.602176634 × 10⁻¹³ joules. This value is exact under the current SI definitions.

How do I convert joules to megaelectronvolts?

Multiply the energy in joules by 6.241509074 × 10¹² (equivalently, divide by 1.602176634 × 10⁻¹³). For instance, 1 J is about 6.24 × 10¹² MeV.

Why is the conversion factor exact?

Since 2019 the elementary charge is defined to be exactly 1.602176634 × 10⁻¹⁹ coulombs. Because an electronvolt is the charge multiplied by one volt, the eV-to-joule relationship — and therefore the MeV-to-joule relationship — carries no measurement uncertainty.

What is the difference between eV, MeV, and J?

An electronvolt (eV) is the energy an electron gains across a one-volt potential. A megaelectronvolt (MeV) is one million eV. The joule (J) is the SI unit of energy and is vastly larger: 1 J equals about 6.24 × 10¹² MeV.

Can I see the result in calories or kilojoules?

Yes. The converter lets you display the joule side in joules, kilojoules, megajoules, or thermochemical calories, so you can read the energy in whichever unit suits your work.

What does a 1 MeV photon’s energy correspond to?

A 1 MeV gamma-ray photon carries 1.602176634 × 10⁻¹³ joules of energy — a typical scale for energetic nuclear gamma rays.