A measure typically determined by the number of theoretical plates (N) calculated from the equation N = 16(V_R/w_b)2 = 16 (t_R/w_b)2, where w_b is the peak width measured at the base. If the peak width is measured at half height, the following equation is used: N = 5.545 (V_R/w_h)2. The plate height (H) or HETP is determined by H = L/N. The efficiency of asymmetric peaks is better determined from the peak centroid and variance by mathematical analysis of the peak shape. See also Foley–Dorsey equation.