Synthesis of spherical ZnO nanoparticles by room temperature chemical precipitation method was scaled up from a batch volume of 200 mL to batch volume of 500 mL, 1 L, 2 L and 5 L. Electron microscopy results reveal spherical morphology of the particles with sizes in the range of 20-40 nm at all batch volumes (scales). X-ray diffraction studies showed that the ZnO nanopowders synthesized at all batch volumes had hexagonal Wurtzite structure with a similar crystallite size. The yield of ZnO nanoparticles increased linearly with batch volume. The scale up results in increased yield at lower time consumption.