The number of theoretical plates; N = 16(t_R/w_b)2, where t_R is retention time and w_b is the base width of the peak. A measure of the efficiency of a column. Sometimes measured as N = 5.54(t_R/w_h)2, where w_h (or w¼) is the peak width at half height. See also efficiency and theoretical plate.

See peak capacity.