The effective plate number

The effective plate number is calculated in the same way as column efficiency, but uses the corrected retention distance, as opposed to the total retention distance in conjunction with the peak width.

As a consequence, the effective plate number is significantly smaller than the number of theoretical plates at low (k') values. The column efficiency and the effective plate number converge to the same value at high (k') values.

It follows, that the effective plate number more nearly corresponds to the actual resolving power of the column. Although the theoretical plate, as defined by the plate theory, has a practical significance and can be used in column design, the concept of the effective plate is not theoretically unsound and is related directly to the theoretical plate.