Knowledge of droplet generation during oxygen blowing, which can be characterized by a blowing number (NB), is crucial for a better understanding of the fundamentals of the kinetics of oxygen steelmaking. A mathematical model has been developed considering the influences of surface tension on the blowing number (NB) using experimental data from Holappa and Jalkanen. The model predicts droplet formation as a function of sulphur and oxygen content in the metal, the temperature profile of the metal bath and lance height. This study includes a sensitivity analysis to investigate the effect of changes in the oxygen concentration throughout the process. 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 the liquid metal. The model also suggests that the variation in oxygen and sulphur contents in the liquid bath has relatively little influence on droplet generation compared to the blowing parameters.