A method for estimating a plurality of geometrical parameters defining the size of a weld gun that has particular application for automatically selecting a weld gun for a welding operation. The method includes iteratively estimating a plurality of geometric parameters based on part section curves corresponding to a direction of approach of the weld gun to weld point of the plurality of weld points. Thereafter, a set of valid weld gun sizes are calculated based on the estimated plurality of geometric parameters. Similarly all the valid weld gun sizes are calculated corresponding to each of the weld gun approach direction. Further, each set of the valid gun sizes are estimated for each of the weld point for the welding operation. Finally, a weld gun for performing the welding operation is selected based on the set of weld gun sizes corresponding to the welding operation.