Knowledge of droplet generation during oxygen blowing, which can be characterized by a blowing number (N_B), is crucial for better understanding of the fundamentals of kinetics of oxygen steelmaking. A mathematical model has been developed considering the influences of surface tension on the blowing number (N_B) using the experimental data from Holappa and Jalkanen. The model predicts the droplet formation as a function of oxygen content in the metal, the temperature profile of the metal bath and the blowing parameters such as lance height and nozzle design. This study includes a sensitivity analysis to investigate the effect of the changes in the oxygen concentration throughout the process. The results from the model are in a good agreement with previous studies on the effects of blowing parameters on the droplet generation. It has been found that the rate of droplet generation increases with increasing jet momentum onto the metal bath and with decreasing surface tension of liquid metal. The model also suggests that the variation in oxygen content in liquid bath has relatively small influence on the droplet generation.