This study investigates the potential core length in the jets which is emitted from circular convergent nozzles. The experimental data from the Free Jet facility are compared and verified with numerical simulations. This research analyzes the potential core length and its impact on jet decay behavior across specific downstream distances. The different pressure data in various locations with respect to the distance were plotted for Mach 0.6 and Mach 1 along the Y-axis and Z-axis, respectively, to show the pressure variation in terms of potential core length. Consistent results from experimental measurements and ANSYS simulations confirm that potential core length and jet decay characteristics vary with respect to the Mach Number. Nozzle design also plays an important role in the decaying of the jet characteristics. These findings provide practical insights for optimizing circular nozzle designs in applications, requiring efficient jet behavior, noise reduction, and thrust improvement.