In the present work, mixing time measurements have been made with jet mixers over a wide range of jet velocities, liquid levels and tank sizes. The nozzle was kept along the axis of the vessel and the nozzle clearance was varied over a wide range. It was observed that the mixing time decreases with an increase in the jet path length (nozzle clearance) for a given tank size and given amount of liquid. The reasons for this behaviour are explained with the help of CFD modelling. The effect of tank diameter has been studied independent of the jet path length. A correlation has been developed for process design. Jet mixers have been compared with impeller-stirred tanks in terms of their energy efficiency. Reasons for the observed behaviour have been provided.