Abstarct: The main aim of the present investigation is to develop correlations to calculate natural gas leakage rate form above-ground and buried urban distribution gas pipelines. By using numerical simulation, has been paid to calculate the amount of natural gas leakage from a small hole located on top of the lateral surface of the above-ground and buried distribution gas pipe lines. The geometry is designed and meshed by Gambit software and then numerical solution is done by using Fluent software. The intended fluid is considered as compressible with ideal gas behavior, flow is turbulent and steady and soil is considered as a porous zone. The results indicate that in the above-ground pipe state, for holes with small diameters, discharge speed reaches to the sound speed and at the so-called, choking occurs in the flow. Also baxsed on the result, the volumetric flow rate of leaked gas have a linear relation, second order relation and fourth order relation with pressure of initial point, diameter of hole and ratio of the hole diameter to the pipe diameter, respectively. In the case of buried pipes, permeation depth of gas into soil at the small diameter holes is more than large holes but volumetric rate of leaked gas is lower. Finally two useful correlations have been proposed to calculate the natural gas leakage from a small hole located on the lateral surface of the above-ground and buried distribution gas pipelines.