A simple yet accurate homogenization method is developed to model the effective elastic and transport properties of fiber and particulate composites. This model can fit perfectly with experimental or numerical data for a large range of the inclusion volume fraction just by calibrating a single micro-structural parameter. The latter is pre-calibrated in this paper for some typical structured or randomly distributed microstructures. In practice, it can be obtained for any arbitrary microstructure if one or several data points are available. The simplicity and the accuracy of the proposed method make it superior to the classical methods in literature such as the Hashin’s composite sphere assemblage, the Mori-Tanaka scheme, the self-consistent scheme, the generalized self-consistent model and the Torquato’s statistical third order approximation. In this very first attempt, only the isotropic particulate composites and the transversely isotropic fiber composites are considered.