In 1977 an expression for the magnetic moment of a massive Dirac neutrino was deduced in the context of electroweak interactions at the one-loop level. A linear dependence on the neutrino mass was found. Alternatively, a magnetic moment for a massive neutrino arising from gravitational origin is predicted by the so-called Wilson-Blackett law. The latter relation may also be deduced from a gravitomagnetic interpretation of the Einstein equations. Both formulas for the magnetic moment can be combined, yielding a value for the smallest neutrino mass m₁.

The gravitomagnetic moment, i.e., the magnetic moment from gravitational origin, may contain different g-factors for the massive neutrino eigenstates m₁, m₂ and m₃, respectively. Starting from the Dirac equation, a g-factor g = 2 has been deduced for a neutrino in first order, related to the derivation of the g-factor of charged leptons. When a value g = 2 is inserted, a value of 1.530 meV is obtained for the lightest neutrino mass m₁, the main result of this work. The remaining neutrino masses can then be calculated from observed neutrino oscillations. The so-called geometric mean mass relation between the three neutrino masses appears to be in fair agreement with our results. A possible dependence of the neutrino mass on the electroweak coupling constant is discussed.

The neutrino with the smallest mass m₁ may also possess the smallest magnetic moment of all known elementary particles. Its gravitomagnetic formula is a combination of three Planck units.