Fluid flow through random two-dimensional fracture networks is investigated, with the aim of establishing a methodology for estimating the macroscopic effective hydraulic conductivity based on the parameters of the fracture network. A wide range of isotropic networks is examined: the lengths are either uniform, or follow a power law or lognormal distribution; the apertures are either uniform, or proportional to the fracture lengths. A methodology is developed that utilises the fracture density and the aperture distribution, but does not require explicit solution of the flow equations. This method provides an accurate estimate of the macroscopic hydraulic conductivity, for all cases considered, spanning ten orders of magnitude.