The aim of our research was to find out the influence of the composition of shielding gas on costs of the welding joint. We were looking for different mixtures of shielding gas that is used in MAG welding for non-alloyed steel. For economical estimation of welding joint following researches were executed: amount of spatter on the welded parts after welding, metallographic research of welding joint, chemical composition analysis, penetration, and calculation of the welding joint. Each composition of the shielding gas provided different results for each parameter during the investigation. This brought us to the conclusion which gas mixture provides the best quality of the welding joint. During research we found out that the choice of separate shielding gas influences the speed of welding. This parameter makes the difference in calculation of the welding joint. There is also lay-out of the components that influence the costs of the welding joint in our research work.