Recently, optical simulation has attracted more attention in different thin film applications. Each layer’s thickness and refractive index are the most essential simulation parameters. This paper discusses and fits the refractive index of aluminum nitride at different geometrical and physical conditions over a wide wavelength range for optical simulations. This study simplifies the use of aluminum nitride in thin film-simulated applications and devices. Plotted curves and fitted equations with MATLAB scripts for aluminum nitride refractive indices at different conditions will be provided to minimize modeling errors.