Injector design is one of the main challenges for development of direct injection and partially stratified gaseous engines. Characteristics of discharged spray from direct gaseous injector influence on combustion and emissions of these engines. In this work axial and radial (lateral) penetration of transient jet of direct gaseous injector are investigated for different nozzle diameters and different pressure ratios numerically and experimentally. High speed Schlieren imaging method is used for jet visualization and image processing technique is utilized for analyzing the images and extracting jet boundaries and its axial and radial penetrations. Finite volume based software is used for numerical calculations. Measuring of the axial and radial penetrations for different cases referred to in this paper provides more accurate formulation for the mentioned parameters for transient direct injection gaseous jet discharged from the injector. Experimental and numerical findings show that higher axial penetrations for larger diameters of nozzle and higher pressure ratios are achievable. Smaller diameter of nozzle gives higher relative lateral expansion while there is no specific distinction for different pressure ratios. Results show that the ratio of radial to axial penetration for transient jet is decreased by time and reaches to a constant value of $0.33{pm}0.05$ and the normalized jet axial penetration has a linear dependency on the square root of time for all cases with slope of $2.9{pm}0.4$.