We have developed an interactive physics simulation that calculates the optimal gear reduction to minimize travel time of given distances. This calculator accounts for motor torque curves, robot mass, rotational inertia, friction, battery characteristics, among other factors. It outputs an easily readable graph demonstrating the trade-off between gear reduction and travel time for several distances. The calculator is accessible on Github for the source code, and through MyBinder for an in-browser interface. It was created using Python in Jupyter Notebook.