In this work, we present a numerical framework to simulate the three dimensional spherulitic morphology of semi-crystalline polymers under isothermal crystallization. The model extends a previously developed 2D model to 3D using a cubic representative volume element. The influence of four key parameters—the characteristic time tc, the characteristic length Lc, the nucleation exclusion zone Ld, and the maximum nucleation time t⋆—is systematically examined with respect to both crystallization kinetics and morphological development. The results establish clear relationships between the Avrami exponent n, the half-crystallization time t0.5, and the parameters tc, Ld/Lc, and t⋆/tc. To connect simulations with experiments, the distribution of spherulite radii on 2D slices is analyzed, enabling the determination of Lc from the mean spherulite size. This stereological link provides a practical route for reconstructing 3D microstructures from 2D microscopy data.