This calculator converts a mass in unified atomic mass units (u, amu or Da) into its energy equivalent from E = mc². Enter the mass in u; you get the energy in mega-electronvolts and joules and the mass in kilograms.
Formula
E = m c². One unified atomic mass unit is 1.66053906660 × 10⁻²⁷ kg (CODATA 2018), and its energy equivalent is 931.49410242 MeV = 1.49241808560 × 10⁻¹⁰ J. So E (MeV) = m (u) × 931.494.
- m: mass in unified atomic mass units
Worked Example
A mass of 1 u.
- E = 1 × 931.49410242 = 931.494 MeV
- E = 1 × 1.4924180856 × 10⁻¹⁰ J = 1.492418 × 10⁻¹⁰ J
- m = 1 × 1.6605390666 × 10⁻²⁷ kg = 1.660539 × 10⁻²⁷ kg
Limits and common mistakes
- For the energy released in a reaction, enter the mass defect (mass before minus mass after), not a whole atom’s mass.
- Atomic masses from a periodic table are averages over isotopes; use the isotope’s mass for nuclear sums.
- 1 MeV = 1.602176634 × 10⁻¹³ J.
Formula used
in u | Mass | u | 1 | 0 out mev | Energy equivalent | MeV | u * 931.49410242 | 3 out j | Energy equivalent | × 10⁻¹⁰ J | u * 1.4924180856 | 6 out kg | Mass | × 10⁻²⁷ kg | u * 1.6605390666 | 6
Each line is one input (in, sel, list) or one result (out: label, unit, formula, decimals). How the calculators work
Method: the standard formula for this calculation, rounded as each result states. See how the calculators work or report an error.
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