The DLVO theory has been widely used to study the stability of colloidal systems with the van der Waals interactions modeled according to the Hamaker (microscopic) theory. The Hamaker theory, in addition to neglecting many-body interactions, does not account for retardation effects. Retardation effects can be included within the framework of the microscopic theory. For spherical particles, an "exact" expression has been derived by Clayfield et al. Lifshitz (macroscopic) theory, on the other hand, accounts for both many-body and retardation effects but is computationally intensive and requires dielectric data at different frequencies. For spherical particles, it is not practical to use the "exact" expression for van der Waals interaction derived by Langbein; therefore approximations have to be used. Approximate expressions to calculate the van der Waals interaction energy between spheres were considered in terms of accuracy, ease of computation, and required material parameters with the "exact" expression derived by Langbein used as the benchmark. It was found that the "exact" expression using the microscopic theory works as well as the best approximation to the macroscopic theory.