All pH calculations for simple acid-base systems used in introductory courses on general or analytical chemistry can be carried out by using a general procedure requiring the use of predominance diagrams. In particular, the pH is calculated as the sum of an independent term equaling the average pK[subscript a] values of the acids involved in the diagram step and a concentration-dependent value, calculated as the ratio between ?pC (that is, -log C[subscript acid] + log C[subscript base], corresponding to the predominant species involved in the predominance diagram step) and the number of pH-controlling acid-base pairs involved in the diagram step (one or two for conjugate or nonconjugate systems, respectively). A number of acid--base features can be readily explained via this procedure. This methodology can be extended to complexation equilibria.