Precise measurements of net endogenous acid production (NEAP) to determine net acid balance require labor and laboratory intensive steady-state measurements of dietary nutrient intakes and urine and stool composition. In an effort to simplify the task, investigators have devised several alternative methodologies, especially computational predictive models based on diet composition. This paper describes the so-called gold standard, and the details of each alternative methodology, discussing their strengths and potential pitfalls. We also briefly discuss what we believe the optimal NEAP for adult humans, and how to achieve that through diet.