Density Functional Theory was used to calculate and correlate 14 ESR, NQR, Reflectance and Magnetic parameters of 20 Co+2 and Ni+2 complexes such as [CoX4]2- (X = F, Cl , Br ,I), [Co(OH2)4]2+, [Co(NCO)4]2-, [CoX6]4- (X = F, Cl), [NiX4]2- (X = Cl ,Br, I, NCO), [NiX6]4- (X=F, Cl ,Br, I) [Ni(H2O)6]2+, [Ni(NH3)6]2+, [Ni(CH3NH2)6]2+, [Ni(NH3)4(NCS)2]. All computations were carried out in the gas phase using ADF2010.02 by applying Single Point, LDA, Default , Spin Orbit, Unrestricted, None, Collinear commands using DZ or TPZ basis sets. The complexes were optimized to obtain two ESR (g11, g22, g33, giso, a11, a22, a33, Aten) and three NQR parameters [?, q11, q22, q33, NQCC]. Two Reflectance parameters [?complex, % covalent character] were calculated from giso. In addition, five magnetic [?soc, ?t, ?net, t2g electron delocalization and its constant k] and two more ESR [H^, __ampersandsignDelta;E hf] parameters were calculated by combining the ESR and Reflectance data. We verified the Laplace equation using the NQR data. The delocalization parameter (k) and the reflectance parameter called Nephelauxetic ratio (?35) were found to have almost the same values as both determine the covalence in complexes. The calculated values of parameters were found in agreement with their reported values.