The theoretical approach for calculations of fractal-like particles characteristics on the basis of gas-kinetic results for homogeneous spheres is presented. It consists in replacement of a real fractal aggregate by an equivalent sphere with the mobility radius and approximations of the density and heat conductivity of the aggregate by their effective values. The validity of the method has been confirmed in the comparison with the known experimental data. The theory suggested has two important restrictions: fractal aggregate should consist from a great number of primary particles (100 and more) and primary particles should be monodisperse. Violation of these conditions leads to considerable divergence between theoretical and experimental results.