The influence of the geometry, via the ratio L/W of the Hall cells and the geometrical correction factor G on several figures of merit regarding Hall sensors is analyzed, namely the sensitivity, Hall Voltage and power dissipated within the device. Experimental values for the parameters of interest are given for eight different geometries integrated in CMOS technology using certain biasing currents. We discuss how these results compare with an analytical model and we propose a global optimization analysis for guiding the designer in best Hall cell dimensions selection.