Entrainment of liquid droplets in vapor or gas is frequently encountered in gas-liquid contactors and in vapor generators, such as reboilers, evaporators, trays of distillation column, etc. , due to an incomplete separation of the two phases when the vapor leaves the liquid. Entrainment lowers the efficiency of the equipment as well as the quality or purity of the product. The authors have done a dimensional analysis of the variables involved and carried out experiments to evolve a correlation. The dimensionless correlation so obtained is given.