# Nuclear magneton

The nuclear magneton (symbol μN), is a physical constant of magnetic moment, defined in SI units by:

$\mu_\mathrm{N} = {{e \hbar} \over {2 m_\mathrm{p}}}$

and in Gaussian CGS units by:

$\mu_\mathrm{N} = {{e \hbar} \over{2 m_\mathrm{p}c}}$

where:

e is the elementary charge,
ħ is the reduced Planck constant,
mp is the proton rest mass, and
c is the speed of light

In SI units, its value is approximately:

μN = 5.05078353(11)×10−27 J/T

In Gaussian CGS units, its value can be given in convenient units as

μN = 0.105155 efm

The nuclear magneton is the natural unit for expressing magnetic dipole moments of heavy particles such as nucleons and atomic nuclei.

The magnetic dipole moment of the electron, which is much larger as a consequence of much larger charge-to-mass ratio, is usually expressed in units of the Bohr magneton.