# Topics - Plate Number

**plate number**of the column. It is a measure of the capacity of the column for restraining peak dispersion. The higher the plate number of the column, the more narrow the peaks. The plate number is calculated as 16 times the square of the ratio of the retention distance (the distance between the injection point and the peak maximum) to the peak width at the points of inflection (the points of inflection occur at 0.6065 of the peak height). The plate number has a maximum value at a particular mobile phase velocity called the

**optimum mobile phase velocity**.