Non-covalent interactions (NCIs) between a ligand and its target are critical for dictation of binding affinity. Electrostatic interactions are strong NCIs and have significant influence over binding affinity. By matching the 3D ESP surfaces of a target and ligand, we can qualitatively estimate the strength of such interactions. To obtain a quantitative result, the electrostatic complementarity score is calculated from ESP surfaces of a drug-target interface, either experimentally or computationally. ESP calculated from quantum chemical methods such as density functional theory (DFT) has been proven to be on par with experimental methods. Although the DFT method is robust and effective compared to experimental ones, its high computational cost makes it impossible to be applied to biomolecules or to be used as a high-throughput screening method. Molecular mechanic force field (MMFF), on the other hand, while much cheaper, is a significantly less accurate approach. In MMFF, important polarization effects, such as lone-pair electrons or σ-holes, cannot be precisely represented by simple atom-centered charges. Furthermore, certain charge parameters for ligand force fields are only available through extra QM calculations.