Height Equivalent to the Theoretical Plate. Numerically equal to column length divided by the number of theoretical plates in the column. The HETP is the theoretical link between the Plate Theory and the Rate Theory as the HETP is numerically equal to the variance per unit length of the column as determined from the Rate Theory. As the HETP is a function of both the properties of the column and the solute, it will vary from one column to another and, more importantly, between different solutes eluted from the same column in the same chromatogram. See Plate Theory and Rate Theory.