Minimizing wave drag is critical to successful and efficient transonic and supersonic flight. Area-ruling is the process of managing the cross-sectional area of an aircraft to lessen the wave drag experienced in flight. Effectively calculating the necessary areas for a given aircraft can be difficult, and existing tools for conducting a wave drag analysis often carry limitations in both functionality and availability. In this work, the author utilized an existing parametric geometry tool named OpenVSP to create an interactive design tool for approximating zero-lift wave drag. Here, the wave drag calculation methodology used in industry for decades is combined with the powerful geometry engine of OpenVSP, which was recently heavily upgraded at the start of 2015. Various visual aids allow users of this OpenVSP wave drag tool to interact with area and wave drag results and develop intuition for supersonic aircraft design using the area rule approach. OpenVSP allows geometry changes to be made quickly, enabling rapid reanalysis by the wave drag tool for expeditious comparison of results across the design space.