A theoretical and experimental approach to computing the droplet transfer frequency in gas metal arc welding is discussed. In this study, welding experiments using a 0.045" diameter, ER70S-6 manganese steel wire were conducted to examine the droplet transfer mechanism using high-speed photography. Changes in both energy and mass inputs to the electrode occur during process control and their transient conditions have significant effects on the transfer frequency. To. develop a more accurate model for the transfer frequency, both the mass conservation and energy balance theories were combined into one model. Such a combined model is more appropriate and suitable for process control and it gives a three-dimensional relationship between transfer frequency, energy and droplet diameter. Knowing this relationship, control of transfer frequency can be implemented to obtain a desired droplet diameter.