In this paper we present a new method for real time estimation of the sail boat polar diagrams. The idea of the algorithm is principally based on the standard procedure used to select the best route that guarantees the major boat speed during a sail competition. The method is focused on a continuous comparison of the navigation data with the optimal polar diagram computed until then. The optimal surface is real time updated if the best performances reached are overcome. The outcome is the Real Time Polar Diagram, that describe the real performance of a sailboat with more accuracy with respect to the maps provided by VPPs. The feasibility of the method is tested on simulations and experimental data collected with an America's Cup Class and amateur sailboat.