The density of nine binary and two ternary liquid mixtures at different temperatures, pressures, and compositions has been calculated using a new equation of state considering mean geometry approximation "MGA". Although the studied mixtures cover the vast variety of mixtures including the inert gases, polar, nonpolar, refrigerant, and strongly hydrogen-bonded systems, the results in prediction of density show good agreement with experiment. The excellent results have been obtained whenever the size and the strength of intermolecular forces of components in a mixture are very similar. Our results show that the effect of size is more important than that of the strength of intermolecular forces. Since the strength of hydrogen bonding in the system of water/methanol is very high, the agreement of calculated densities with the corresponding experimental values is interesting for which the average absolute deviations are better than 1%. To show the ability of this equation of state in prediction of density, the calculated densities of some liquid mixtures have been compared with those of computed from other equations of state. (c) 2006 Elsevier B.V. All rights reserved.