  We present a self consistent method based on cluster algorithms and
Renormalization Group on the lattice to study critical systems numerically. We
illustrate it by means of the 2D Ising model. We compute the critical exponents
$\nu$ and $\eta$ and the renormalization group flow of the probability density
function of the magnetization. The results, compared to the standard Monte
Carlo Renormalization Group proposed by Swendsen [1], are very accurate and the
method works faster by a factor which grows monotonically with the lattice
size. This allows to simulate larger lattices in reachable computational times.
