A microstructure modeling program was conducted to establish a recrystallization database and grain size simulation package for the ingot to billet reduction of alloy 718. Ingot preparation used full-sized ingots of aerospace-engine quality chemistry and processing. The recrystallization database was populated with data collected from large-sized samples, extracted from critical ingot locations and subjected to isothermal hot compression testing. The microstructure simulation package was developed based on finite element deformation characterization and rate-equation microstructure methodology. This approach resulted in accurate modeling of the microstructure produced in hot compression tests of the ingot material.