Size control of nanoparticles requires precision control of particle nucleation and growth. For the understanding of the particle nucleation process, a novel approach to model the nucleation phase in crystallization will be presented. This approach is based on the balanced nucleation and growth (BNG) model, which is relatively simple, and allows modeling for any college or university level with standard mathematical computer programs, e.g., MS EXCEL. The BNG model shares the concept of critical nucleus size with the classical nucleation model (Doering - DB). It differs from the DB model by calculating the nucleation rate as a function of nucleation time. In contrast, the DB model uses a single Arrhenius derived nucleation rate with supersaturation as the single adjustable control variable. The BNG model uses for independent modeling input parameters, which are the reaction rate of the formation of crystals from starting materials, Fn, the size of the critical nucleus, rc, the reactant addition rate during nucleation, R, and the maximum crystal growth rate, Gm. Of these, rc is based on fundamental science, and Fn, R, and Gm are independently accessible experimental parameters. Results will be presented of the nucleation rate and population growth rate during the crystallization phase as a function of time. These allow determining the total nucleation time, the total number of crystals formed, and number and size distribution as a function of the four model parameters.