# Amu To Kg

- In imprecise terms, one AMU is the average of the proton rest mass and the neutron rest mass. This is approximately 1.67377 x 10 -27 kilogram (kg), or 1.67377 x 10 -24 gram (g). The mass of an atom in AMU is roughly equal to the sum of the number of protons and neutrons in the nucleus.
- In related terms, another unit of mass often used is Dalton (Da) or unified atomic mass unit (u) when describing atomic masses and molecular masses. It is defined to be 1/12 of the mass of one atom of carbon-12 and in older works is also abbreviated as 'amu'. Also, important in this field is Avogadro's number (N A) or Avogadro's constant (6.
- Definition and details for atomic mass unit (amu): Atomic mass unit (u or amu) is a unit of mass used by chemists and physicists for measuring masses of atoms and molecules. In 1960 it was defined as 1/12 of the mass of the carbon-12 atom. This unit is approximately 1.66x10 -27 kg.
- One unified atomic mass unit is about the mass of one nucleon (either a single proton or neutron) and equivalent to 1 g/mol. Kilogram (abbreviations: kg, or kgm ): is a SI (metric) system unit of mass (IPK, also known as 'Le Grand K' or 'Big K') and equivalent to 1/1000 of one gram.

1 kilogram is equal to 6.949E+26 amu. Note that rounding errors may occur, so always check the results. Use this page to learn how to convert between kilograms and atomic mass units. Type in your own numbers in the form to convert the units!

### Convert 1 amu to MeV

**Solution:**

1) Determine mass of 1 amu (in kg):

By definition, the mass of 1 atom of C-12 is 12 amu.Therefore, the mass of one mole of C-12 atoms is, by definition, 12 g

Avogadro's Number is 6.0221409 x 10^{23} mol¯^{1}

12 g/mol / 6.0221409 x 10^{23} mol¯^{1} = 1.9926468 x 10¯^{23} g (mass of one atom of C-12 in g)

(1.9926468 x 10¯^{23} g) (1 kg / 1000 g) = 1.9926468 x 10¯^{26} kg (mass of one atom of C-12 in kg)

1.9926468 x 10¯^{26} kg/atom / 12 amu/atom = 1.660539 x 10¯^{27} kg/amu (this is the mass of 1 amu)

2) Use Einstein's mass-energy equation to determine Joules in one amu:

E = mc^{2}

E = (1.660539 x 10¯^{27} kg) (2.99792458 x 10^{8} m/s)^{2}

E = 1.49242 x 10¯^{10} kg-m^{2}/s^{2} (this is Joules)

3) Convert J to eV, then MeV

1 eV = 1.60217733 x 10¯^{19}J

1.49242 x 10¯^{10} J / 1.60217733 x 10¯^{19} J/eV = 931494893 eV

(931494893 eV) (1 MeV / 10^{6} eV) = 931.494893 MeV

Often, 931.5 MeV is the value used in problem solving.

4) 931.5 MeV is the __energy__ in one amu. Is it possible to express the mass of one amu using MeV in some way? I'm glad you asked:

## How To Convert Kg To Amu

^{2}

931.5 MeV = mc^{2}

m = 931.5 MeV/c^{2}

The use of 931.5 MeV/c^{2} for the mass of 1 u is wide-spread. So much so that the c^{2} is often not written and you must infer its presence by context.

5) To sum up:

1 u = 931.5 MeV (expressed as energy)1 u = 931.5 MeV/c^{2} (expressed as mass)

In solving problems, you may see this unit:

931.5 MeV/u-c^{2}

read it as 931.5 MeV/c^{2} per 1 u

By the way, if you look around the Internet, you will find values different than the 931.494893 value I calculated. This is because different authors will use values that they have rounded off differently than the ones I used.

For example, I used 1.660539 x 10¯^{27} kg for the mass of 1 amu. Often, you will see it as 1.66 x 10¯^{27} kg.

The cumulative effect of these rounding off decisions will be seen in slightly different answers from different authors.

Please provide values below to convert Atomic mass unit [u] to kilogram [kg], or *vice versa*.

### Atomic Mass Unit to Kilogram Conversion Table

Atomic Mass Unit [u] | Kilogram [kg] |
---|---|

0.01 u | 1.6605402E-29 kg |

0.1 u | 1.6605402E-28 kg |

1 u | 1.6605402E-27 kg |

2 u | 3.3210804E-27 kg |

3 u | 4.9816206E-27 kg |

5 u | 8.3027009999999E-27 kg |

10 u | 1.6605402E-26 kg |

20 u | 3.3210804E-26 kg |

50 u | 8.3027009999999E-26 kg |

100 u | 1.6605402E-25 kg |

1000 u | 1.6605402E-24 kg |

### How to Convert Atomic Mass Unit to Kilogram

1 u = 1.6605402E-27 kg

1 kg = 6.0221366516752E+26 u

**Example:** convert 15 u to kg:

15 u = 15 × 1.6605402E-27 kg = 2.4908103E-26 kg