This paper investigates the average dielectric permittivity (-ε) in the Maier-Meier theory for calculating the dielectric anisotropy (△ε) of nematic liquid crystals. For the reason that e of nematics has the same expression as the dielectric permittivity of the isotropic state, the Onsager equation for isotropic dielectric was used to calculate it. The computed -ε shows reasonable agreement with the results of the numerical methods used in the literature. Molecular parameters, such as the polarizability and its anisotropy, the dipole moment and its angle with the molecular long axis,were taken from semi-empirical quantum chemistry (MOCPAC/AM1) modeling. The calculated values of Ae according to the Maier-Meier equation are in good agreement with the experimental results for the investigated compounds having different core structures and polar substituents.