In this work, I present a straightforward approach for computing surface free energy γF based on the assessment of surface internal energy (γU), avoiding the difficulty connected to the determination of the elastic contribution in the case of a solid surface. This methodology has thus been extended to the calculation of γF for the interface between the liquid–vapor phase of water, the solid–vapor interface of aluminum, the aluminum–water interface, rigid graphene–water solid–liquid interfaces, and the n-dodecane–water liquid–liquid interface.