Theoretical plate number (N)
The column efficiency can be measured as theoretical plate number (N). This is a measure of relative peak broadening (or peak width) for an analyte in separation. The theoretical plate number is measured by comparing the retention time (tR) and the peak width (w). There are 2 formulas that one can used to measure the theoretical plate number, depending if you know the peak width (w) or half of the peak width (w1/2).
Higher plate number gives sharper and narrower bands leading to better detection and better peak capacity to resolve complex samples. The theoretical plate number increases when using a smaller bead size. Using a smaller bead size also has its benefits, such as improving the resolution as well as decreasing the run time. However when using a smaller bead size, higher pressure is reached.