Ab initio calculations are computational chemistry methods that predict molecular properties based on quantum mechanics principles without any empirical data. The dipole moment of a water molecule H2O can be calculated using ab initio methods, such as the Hartree-Fock method or more advanced methods like Mller-Plesset perturbation theory MP2 and coupled-cluster theory CCSD T .According to ab initio calculations, the dipole moment of a water molecule is approximately 1.85 Debye. This value may vary slightly depending on the level of theory and basis set used in the calculations.The experimentally measured dipole moment of a water molecule is around 1.85 Debye as well, which is in good agreement with the ab initio calculations. This demonstrates the accuracy of ab initio methods in predicting molecular properties like the dipole moment.