The chemical bath deposition of nanowires is of high interest for a wide variety of optoelectronic, piezoelectric, and sensing devices, but a theoretical description of the elongation process is still missing despite its critical importance. By solving Fick's diffusion equations in combination with thermodynamic computations, we determine the expression of the axial growth rate of nanowires and its temporal dependence under dynamic conditions, namely in a sealed reactor where the depletion of chemical reactants occurs. The theoretical model is found to be in very good agreement with a large set of experimental data specifically collected in the case of the chemical bath deposition of ZnO nanowires. In particular, an activation energy of 198 ± 24 kJ/mol is deduced for the elongation process of ZnO nanowires, involving the energy barriers for both the dehydration process of Zn(II) species (i.e. [Zn(H2O)6] 2+ ions) and their subsequent direct incorporation onto the c-plane top faces. This shows its high potential for deeply investigating the physicochemical processes at work in the chemical bath. By using the theoretical model as a predictive approach, a complete growth diagram reporting the evolution of the length of ZnO nanowires vs effective growth time and temperature is also gained over a broad range of conditions, revealing its additional high potential for applied research and industrial purposes. The present general approach is further compatible with a broad range of chemicals in solution and of semiconducting materials grown by chemical bath deposition. predictive behavior in a broad range of CBD conditions for applied research and industrial purposes. Eventually, this general approach is of high potential for other systems involving a wide variety of chemicals in solution and of semiconducting materials grown by CBD. SUPPORTING INFORMATION Detailed proof of the dynamic growth model, pictures of the chemical bath, top-view FESEM images of the series at 90 °C with 800 mM of NH3, cross-sectonial view FESEM images of the series at 80 and 95 °C, NW length and numerical values of the series at 80, 90 and 95 °C (PDF).