  We propose a new numerical method to determine the central charge of the
conformal field theory models corresponding to the 2D lattice models. In this
method, the free energy of the lattice model on the torus is calculated by the
Wang-Landau algorithm and then the central charge is obtained from a free
energy scaling with respect to the torus radii. The method is applied for
determination of the central charge in the site-diluted Ising model.
