This paper presents an experimental study on various input parameters to optimize the dilution percentage of stainless steel 409L plates by using metal inert gas welding (MIG). Dilution represents the proportion of base material melted to the entire cross-sectional area of the fusion zone. A mathematical equation was generated using the design matrix to obtain an optimized parametric combination of input parameters. Further, the adequacy and the significance of the generated equation were verified using F-test & T-test, respectively. In the graphical analysis performed using response surface methodology (RSM) it was inferred “Wire feed rate”, “welding speed” and “voltage” came out to as input parameter which showed a profound effect on dilution. The results show that the proposed method, mathematically agrees well with the definition of weld dilution. It was inferred increasing dilution to a level higher than the critical value; the weld can be concentrated as well when the filler wire is rich in the same composition as the substrate does.