The scale-up of a micro-reactor with a mixer designed for liquid-liquid reactions is investigated using a 3/7th approach that scales the hydraulic diameter at increased flow rates and keeps constant the average rate of energy dissipation. Smaller (d(h) 283 um) and larger-scale (dh 714 um) mixers are compared using single phase pressure drop measurements and a liquid-liquid reactive extraction. The single phase tests demonstrate that the energy dissipation rate of the larger scale mixer is comparable to the smaller scale mixer at flow rates similar to 8.5 times greater. The overall volumetric mass transfer coefficients of the reactive extraction, K(c)a, of both scale mixers were also similar at equal energy dissipation rate in the drop flow regime. Finally, the upper limit of the sizing approach is discussed and compared with commercially available static mixers. (C) 2015 Elsevier Ltd. All rights reserved.