Convert Units of Atomic Mass

Calculator for converting the atomic mass unit u to MeV/c², yoctogram, and kilogram. Atomic masses are usually measured in the atomic mass unit u. 1 u is defined as one-twelfth of the mass of the carbon isotope C¹² and corresponds to 1.660539069*10^-26 kilograms. The conversion factor from u to grams is the mole, which is 6.02214076*10²³ particles. This number of particles with 1 u mass equals one gram. yg stands for yoctogram, which is 10^-24 grams. 1 u has 1.660539069 yoctograms. 1000 yg are 1 zg, zeptogram.
Electronvolt (eV) is a unit of energy. Energy can be converted into mass using the famous formula from Einstein's special theory of relativity. MeV/c² is a unit of mass and means megaelectronvolts per square of the speed of light. 1 u corresponds to 931.49410372 MeV/c² (CODATA 2018).

Please specify one of the four masses to calculate the other three. When specifying kilograms, please also include the power factor; in the range of u, this is -26. The kilogram is therefore a much larger unit than the other three mass units.

Example: The water molecule H₂O has an atomic mass of 18.015268 u. This corresponds to 16781.116 MeV/c² or 16.781116 GeV/c² (gigaelectronvolts per square of the speed of light). That is 29.915 yoctograms or 2.992*10^-26 kilograms.

The u stands for unified atomic mass unit. The symbol Da for Dalton, named after John Dalton, is sometimes used for the atomic mass unit. u is not an SI unit, but is approved for use with the SI. The same applies to the electronvolt and its derived unit MeV/c². The SI unit of mass is the kilogram; one kilogram is equal to 1000 grams or 10²⁷ yoctograms.