During product changes in extrusion applications a high amount of material, energy and production time is lost for the process. This effect is amplified by increasing numbers of color and material changes due to decreasing lot sizes. Therefore a numerical approach based on empirical data is used to quantitatively determine the product changing behavior in complex extrusion die geometries. The suggested method thus not only allows the optimization of the die geometry aiming at equal residence time distributions but also enables the evaluation of cases at different operational points and with different materials as changing partners. The presented approach is based on the assumption that although it is common practice to calculate fluid dynamic problems with zero wall velocity, in reality a finite flow velocity at the wall has to exist in order to enable a complete change of the materials in the channel to finish. The specific velocities at the wall as location of the highest residence time in the channel are calculated from a correlation between the viscosity ratio of the changing partners and empirical data of completed material changes. The experiments for the data basis are performed on a basic round strand die geometry and the materials used are LDPE types of different viscosity levels at nearly similar behavior regarding the fluid dynamical properties. The complex die geometry is described in a model by using a commercial CFD-software in which the multiphase approach supports the volume of fluid method (VOF). The calculation of the wall velocity is implemented with a user defined function (UDF) including also the behavior of the materials described in form of the carreau law.