Mass-Energy Equivalence Calculator Formula

Understand the math behind the mass-energy equivalence calculator. Each variable explained with a worked example.

Use the Mass-Energy Equivalence Calculator

Formulas Used

Energy

energy_j = mass * pow(2.998e8, 2)

Energy (MeV)

energy_mev = mass * pow(2.998e8, 2) / 1.602e-13

Energy (kWh)

energy_kwh = mass * pow(2.998e8, 2) / 3.6e6

Variables

VariableDescriptionDefault
massMass(kg)1

How It Works

Mass-Energy Equivalence

Einstein showed that mass and energy are interchangeable, related by the speed of light squared.

Formula

E = mc^2

  • *m* = mass in kg
  • *c* = 2.998 x 10^8 m/s

    • One kilogram of matter, if fully converted to energy, yields about 9 x 10^16 joules, roughly the energy of a 21-megaton nuclear weapon.

    Worked Example

    Energy equivalent of 1 kg.

    mass = 1
    1. 01E = mc^2
    2. 02E = 1 * (2.998e8)^2
    3. 03E = 8.988e16 J
    4. 04E = 2.497e10 kWh = 25 billion kWh

    Frequently Asked Questions

    Can mass really be converted entirely to energy?

    Yes, in matter-antimatter annihilation. An electron meeting a positron converts 100% of their mass to gamma-ray photons. Nuclear reactions convert less than 1%.

    How much energy is in an electron's mass?

    The electron rest mass (9.109e-31 kg) corresponds to 0.511 MeV, a key value in particle physics.

    Is mass created from energy possible?

    Yes. Pair production creates a particle-antiparticle pair from a high-energy photon (near a nucleus to conserve momentum).

    Ready to run the numbers?

    Open Mass-Energy Equivalence Calculator