A correlation of the average drop size in a rotating disc contractor is presented. The rotating disc contactors were studied under various conditions. Various items of importance are system physical properties, column geometry, disc speed and hole distributor diameter. Two systems water (continuous phase)/acetic acid/toluene (dispersed phase) and water (continuous phase)/succinic acid/n-butanol (dispersed phase) were used to give correlation. The correlation was fitted by software. The R-squared and Durbin-Watson state in this prediction are about 95% and 1.82, respectively. The average absolute value of the relative error, AARE, is about 2.2%.