Longitudinal velocity-derivative skewness S0 is directly proportional to the rate of enstrophy generation and hence is a key parameter for characterizing small-scale turbulence. Obtaining S0 requires accurate measurements of the finest scales in the dissipation subrange. In this paper we define a derivative skewness of the inertial range scales that is readily accessible experimentally, and we derive its value analytically. The results depend on the filtering procedure of small scales. Analytically derived inertial range skewness is compared with those computed by high-resolution numerical simulations and obtained in laboratory and field experiments. An alternative definition of the derivative skewness in the full and the inertial range scales is examined to identify the effects of intermittency.