This paper is complementary to the paper ''Gravity in Particle Physics,'' which appeared earlier in this Journal. The present paper contains a more accurate and complete calculation of the rest energies of the most important so-called elementary particles. The rest energies for all leptons, quarks, the proton, neutron, the electroweak and Higgs bosons are calculated with high precision from very simple equations as a function of mainly electric parameters. The values obtained for the Higgs boson, quarks, and neutrinos are predicted values because they still have to be measured, when possible.