An exponential function shortcut calculation (EFSC) method is proposed for the estimation of the number of theoretical plates, N-T, in distillation units. We set up the new concept of the thermal state equation, beta-line equation, and define the cut ratio of the q line, delta, as an independent variable to interpret the stage separating capacity. The EFSC model is established on the basic data of N-T calculated by the previously presented exponential function rigorous calculation (EFRC) method. The data sources of the EFSC method are much greater than those of the Gilliland correlation. The curves of the EFSC model go through the points (X = 0, Y = 1) and (X = 1, Y = 0), whose physical significance fully coincides with the characteristics of R similar to N-T. Validation of the EFSC method indicates that its accuracy is close to that of the plate-to-plate calculations and the EFRC method and higher than that of the Gilliland correlation.