We present a resource-saving algorithm for numerical evaluation of the absolute permeability of a rock from the samples CT-images of huge size, which makes it possible to perform such an assessment using limited computing resources, in particular, personal computers. It is based on a decomposition of the 3D sample image into small representative sub-samples, for which the absolute permeability is estimated based on the numerical solution of the Stokes equation in a static formulation, followed by a creation of the functional dependencies between the permeability and open porosity. After that these dependencies can be extended to the entire original sample or to the full-sized core sample.