Equilibrator is a Microsoft Excel program for learning about chemical equilibria through modeling, similar in function to EQS4WIN, which is no longer supported and does not work well with newer Windows operating systems. Similar to EQS4WIN, Equilibrator allows the user to define a system with temperature, initial moles, and then either total pressure or volume. Unlike EQS4WIN, Equilibrator is designed to let the user find the point of equilibrium using a slider to shift the extent of reaction. The program simultaneously calculates the reaction quotient, the Gibbs free energy, "G", and "[delta]G"; and immediately updates pertinent graphs for feedback. With so many simultaneous ways to evaluate the position of the reaction with regard to equilibrium, Equilibrator is a superior pedagogical tool for helping students truly understand the basic principles of chemical equilibria. (Contains 3 figures and 3 notes.)