Estimating efficiency of an operating column has to be distinguished from that of a column being designed. This crucial point has been totally overlooked in the literature. All the methods and models available for predicting the Murphree efficiencies of tray columns have been developed for the design case. They generate their own mass and heat transfer rates and empirical parameters rather than produce true transfer rates by using operating column (realistic) data, especially the specifications of outlet streams. In addition, most of these methods are limited in application and insufficient in accuracy, especially if applied outside the range of conditions under which they were formulated. The present work introduces a general and applicable method for determining the overall Murphree component efficiencies of an operating tray column. This method uses the specifications of both inlet (feed) and outlet (product) streams of an operating column to back-calculate realistic mass and heat transfer rates for Murphree efficiency estimation. The presented method is usable to operating tray columns with any amount of flow rates and diameter as well as with any number of components and trays. Overall, it can be usable to the gas liquid operating columns filled with any type of trays. (C) 2014 Elsevier B.V. All rights reserved.