The nuclear magneton (symbol μ_p), is a physical constant of magnetic moment, defined by:

where:

e is the elementary charge,

is the reduced Planck's constant,

m_p is the proton rest mass

In the SI system of units its value is approximately:

μ_p = 5.050 786 6(17) × 10^-27 J·T^-1

See also proton magnetic moment .