This paper is based on the connection between the p-character of sp n -hybrid orbitals and the angles between them. This connection is exactly presented by the Coulson theorem. The paper, then, discusses the connection between the d-character of d n s-hybrid orbitals and the angles between them. Our calculations show that the formula used in the literature, for determining d-characters of hybrid orbitals based on the angle between them, has a number of shortcomings. Using the mentioned formula we got contradictory results both in real molecules and hypothetical models. We introduced the concept of ˝non-homogeneous˝ hybrid orbitals and other parameters defined in the formula. This new formula, for those species for which we have identified the error in the current formula, gives values of angles which match to experimental values. In this paper, at many points we used computer to calculate, in multimillion iterations, with very little changes of certain parameters, the share of d-orbitals in halfs of hybrid orbitals in given species and thereby adjust the parameters of the new formula to calculating angles. How far is the range of the new formula, and its flexibility, remains to be checked with a large number of experimentally measured angles in other species.