Computation of the neutrino masses and parameter experimentally abound in literature, while little or no attention has been made to determine it theoretically. However, a recent theoretical study sought to determine the masses of the neutrino, but failed to compute the value for the parameter. Hence, this study was aimed at determining theoretically the parameter from neutrino masses addition as predicted with quantum gravitational couplings/effective Majorana dimensionless coupling via spherical symmetry vacuum solution. A seesaw mechanism (ala mode matrix) was adopted; where the SU matrix was diagonalized to get the mass eigen states. The parameter value which is expressed as a function of the three mass eigen states of the neutrino masses, and which also satisfies the experimental constraints was determined theoretically to be 0.06.