This paper develops an advanced modelling framework for predicting the effective elastic constants of polymer-clay nanocomposites. FE-based and analytical (Mori-Tanaka) approaches are adopted (and compared) to account for different material representations of clay particles using the effective particle concept. Both approaches are developed to account for the varying particle composition (component properties, exfoliation level) and particle orientation. An important feature is that both approaches account rigorously for the anisotropy of the effective clay particle. This has not been addressed previously, but it was found to be of great importance for accurate predictions of elastic nanocomposite constants. Thus, the developed modelling approaches can be used by material scientists and engineers for quantitative predictions of the nanocomposite elastic response.