Quantum-chemical computations based on the Hartree-Fock theory have been carried out for a free and impurity-bound hole polarons in SrTiO3 crystal. Comparing hole localization energy versus lattice relaxation energy, the estimation of spontaneous hole self-trapping in the cubic lattice of pure SrTiO3 has been made. The one-site hole spatial configuration has been found to be the only feasible hole geometry in both pure and potassium-doped SrTiO3 crystals after carefully carried out automated geometry optimization. The Delta SCF calculated absorption energy for the potassium-bound hole polaron was found to be equal to 0.35 eV.