Calculating Theoretical Plates N half height

The theoretical plate number N0.5 can be calculated from a chromatogram using the equation below:

N0.5 = 5.54 (tR/w0.5)2

Where tR is retention time and w0.5 is the peak width at half its height. Remember to use the same units (minutes or seconds) for both values (tR and w0.5).