Ultra high-pressure waterjets (UHP-WJ) have been emerging as a viable method for surface texturing, cleaning, and peening of metallic materials. Previous experimental studies have suggested that removal of material can be related to the energy density of the waterjet impinging upon the workpiece, rather than the net energy. The net energy transferred to the workpiece is a function of four key process parameters, namely, (i) orifice diameter, (ii) orifice geometry, (iii) supply pressure, and (iv) traverse rate. The energy density also incorporates jet spreading as well as flow rate and impulse pressure distributions within the waterjet. In this paper, a novel representation of the power distribution within the waterjet is presented, as well as a relationship governing jet-material interaction. Empirical validation on a Ti-6Al-4V titanium alloy is presented, with good correlation noted between the predicted and experimental results.