As shown on the base of literature data, the relation between standard (Em/n°) and conventional standard (Em/n×) potentials of the metal forming ions Mem+ and Men+ in molten halogenides is unambiguously defined by the ratio of ionic moments of solute and solvent salts cations. The equation is derived that makes it possible to calculate true values of standard redox potentials using experimental data on (Em/n×) in various salt solvents. The latter help in solution of important theoretical and practical problems of electrochemistry related to the stability of valent state of ions being in contact with metals and alloys in salt solvents.