An elemental species that bonds oxide and metal at the interface of electronic devices is crucial to the electric properties of the devices. In this study, interface between alumina and metal in general is discussed from a viewpoint of thermodynamics. By introducing a concept of chemical equilibrium and developing a new way of estimating bonding energy at the interface, a novel numerical formula to predict a stable interface bonding species at a metal/alumina interface is proposed. The effectiveness of the formula was examined by experimental results in references. It was revealed that the prediction by the formula agreed quite well with the results reported in the references. The formula uses only basic quantities of pure elements and the formation enthalpy of oxides. Therefore it can be applied for most of metals in the periodic table and is useful for material screening in developing interfaces with particular functions.