The influence of agitation and irradiation time, agitation speed, ultrasound intensity, and hold-up of dispersed phase on the mean Sauter diameter d(32) is analysed for two model liquid-liquid systems and an industrial one. The classic emulsification method was used applying mechanical mixer as well as ultrasonic energy. Droplet size in dispersed phase was measured using a photographic method. Basing on the obtained results, equations correlating the mean droplet diameter d(32) were proposed, which enable calculating the specific interfacial surface area. The equations obtained have been compared with those available in literature.