Calcium fortification of nutritional products remains challenging, with sedimentation of insoluble calcium salts being the most commonly encountered challenge. In this study, three calcium salts (i.e., carbonate, citrate and phosphate), with either conventional or micronised particle size distributions were studied for physicochemical, bulk-handling and electrostatic properties. The influence of these differences in particle size on colloidal and suspension stability in a whey protein solution was investigated. Micronised powders had significantly smaller mean particle diameter (D[4,3]) (5.09–15.9 μm) than conventional versions (59–103 μm) (p < 0.05). Micronised salts also displayed greater particle interlocking and therefore displayed very cohesive flow properties. In suspension, the sedimentation rates for the micronised salts (0.52–0.75 μm/s) were significantly lower than conventional salts (3.51–6.66 μm/s) (p < 0.05). This new information provided on the modification of physical properties of calcium salts (i.e., micronisation) is essential in supporting the formulation of nutritional products fortified with insoluble calcium salts.