The question of “How good is good enough?” has yet to be fully answered in regard to the accuracy of simulated icing conditions.  This paper addresses this question in the form of an aerodynamic performance sensitivity to icing cloud parameter variations.  Ice tracings were taken from an existing NASA study that examined the effects of icing parameter variations on ice accretion geometry.   These ice accretions were simulated using SLA, and then aerodynamic testing was conducted at the University of Illinois subsonic wind tunnel.  A sensitivity of aerodynamic performance to icing parameter variations was formed by relating the aerodynamic results of this test to the corresponding icing cloud parameter variations of the NASA study.   To judge the real-world effect of icing cloud parameter variations, this sensitivity was extended from airfoil performance to aircraft performance.  For the conditions of this study, it was found that if V_stall was required to be known within ±0.5 knots, the required accuracy in LWC was ±0.025 g/m³, and in MVD was ±1.1 µm.  For ΔV_stall = ±3 knots, the required accuracy in LWC was ±0.12 g/m³, and in MVD was ±5.5 µm.