A model is proposed which is able to predict the maximum particle packing density (phi(m)) over a wide variety of ceramic suspensions with very large difference in particle size/shape, particle surface chemistry, and solvent chemistry. This model provides a simple method to obtain phi(m) directly through the use of a few viscosity-concentration data for a given colloidal suspension, rather than a best-fitting approach. The model is also capable of predicting the viscosity of a variety of ceramic suspensions under different conditions of shear. A comparison with some existing viscosity model is also presented.