Here, we provided a new approach for computing the maximal possible charge a molecular polycation can carry without being thermodynamically unstable (Q max ). The approach is based on the quadratic approximation of the ionization potentials using the energy expansion in terms of Mulliken's electronegativity and Pearson's hardness. For the conjugated hydrocarbons, Q max can be estimated using Equation , and the value for the molecule is provided as the lowest of those values for different fragmentation pathways. This estimation reduced the computations to calculations of only the molecule's and fragment's electronic energy, ionization potential, and electron affinity. Further, by parametrizing these properties with some molecular descriptors, one can produce analytical approximations for the maximal charges, which is essentially a phase diagram of the thermodynamic stability of molecular polycations. We demonstrated the applicability and efficiency of this approach using the three model systems: linear polyenes, monocyclic annulenes, and helium clusters.