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 theretention 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.