The unrestricted Hartree-Fock (UHF) and hybrid density functional theory (HDFT) calculations have been carried out for manganese oxides. In order to elucidate magnetic properties of the species, the effective exchange integrals (J(ab)) have been obtained by the total energy difference between the highest and lowest spin states. The natural orbital analysis has also been performed for elucidation of symmetry and occupation numbers of the magnetic orbitals.