ESDU 88013 presents a semi-empirical method that improves the traditional approach based on Weissinger's simplified lifting-surface theory which drew parallels with the dihedral contribution to the rolling moment due to sideslip. The method relies on ESDU 74011 to estimate the lift increment due to control deflection (in conjunction with the wing lift-curve slope from ESDU 70011), assumes that it acts at the mid-span of the aileron, and corrects the rolling moment so derived by an empirical factor that allows for the aileron effectiveness. The ranges of wing and control geometry for which the method is validated are given, and it is found to predict the derivative to within 20 per cent for values up to -0.15 and to within 0.03 for numerically higher values. A program of the method is provided with ESDU 88040 as ESDUpac A8840.