Analytical and numerical approaches are used to model a gas metal arc welding (GMAW) process. In order to simulate the detailed aspects of material changes during the process, it is important to implement the correct size and distribution of the heat source. In this study the dimensions of a heat source model in a welding case will be calculated based on experimentally observed weld pool sizes. An analytical approach called ‘discretely distributed point heat source model’ will be used for this purpose as an intermediate stage between the experiments and the numerical model. In the numerical approach, the heat source will be split into two perpendicular 2D ellipsoidal sources that correspond to the double-ellipsoidal heat source model. The third dimension of the heat source will be measured from the top-view of the end crater. WeldSimS and Matlab codes are used for finite element and analytical investigations respectively. Both models were compared and analyzed with respect to similar boundary conditions. Numerical simulations show good agreement with the analytical approach calibrated by actual weld dimensions.