Because of multi-functional properties with high specific surface area, ZnO nano architectures are finding immense utilities in variegated applications viz., sensing, diagnostics, etc. To investigate the concept behind the long and vertical growth of the ZnO nano structures, understanding of surface energy, molecular interaction, their reactions at certain physical environment such as temperature and pressure, etc., is utmost important. The high aspect hexagonal crystal growth inside aqueous chemical solution is rarely explained by researchers. This crystal growth mechanism involves variety of variables such as solute concentrations, seed orientation, reaction rate, other impurities, etc. Based on the experimental observation herein, a theoretical modeling for ZnO crystal vertical growth is proposed and its epitaxial growth rate along with side length and with function of time is investigated. © Springer-Verlag GmbH Germany, part of Springer Nature 2018.