In the last years the interest for magnetic stimulation of the human nervous tissue has increased considerably, because this technique has proved its utility and applicability both as a diagnostic and as a treatment instrument. Research in this domain is aimed at removing some of the disadvantages of the technique: the lack of focalization of the stimulated region and the reduced efficiency of the energetic transfer from the stimulating coil to the tissue. Better stimulation coils can solve these problems. Designing coils is so far a trial-and error process, relying on very compute-intensive simulations. In software, such a simulation has a very high running time (several hours for complicated geometries of the coils). This paper proposes and demonstrates an FPGA- based hardware implementation of this simulation which reduces the computation time by 4 orders of magnitude. Thanks to this powerful tool, some significant improvements in the design of the coils have already been obtained.