Redox calculations have the potential to reinforce important concepts in bioenergetics. The intermediacy of the NAD[superscript +]/NADH couple in the oxidation of food by oxygen, for example, can be brought out by such calculations. In practice, students have great difficulty and, even when adept at the calculations, frequently do not understand their significance. The causes of this problem are identified with 1) the context in which redox calculations are presented and 2) the confusion over the formalism of the redox potential, particularly the meaning of the sign that refers to direction of current flow but is frequently confused with thermodynamic sign. A method is described for teaching redox calculations that is straight-forward and simple for students to perform but, at the same time, brings out the key concepts. The primacy of the free energy is emphasized and the method is used to reinforce an understanding of respiration.