Abstract: All aircraft, military and commercial, must satisfy controllability and in turn, maneuverability prerequisites to be espoused by the military or certified for transport aircraft. So, it is imperative for the designers to assess the control authority of candidate configurations early in the preliminary design phase. This early assessment formulates the design process very proficient and cost-effective. Aileron sizing is one of the controllability concepts that should be involved in the preliminary design process. Adding aileron sizing module as a helpful tool for aeronautical students enhance their knowledge, understanding and analyzing studies. This study presents a programmable algorithm for aileron sizing to be employed in any preliminary aircraft design software. The study introduced the necessary formulae as a guide to size the aileron to achieve the prerequisites of the roll control. A solved example has been added to explain the application of the algorithm.