This document specifies three methods (two titrimetric and one potentiometric) for the determination of acidity in animal and vegetable fats and oils, hereinafter referred to as "fats". The acidity is expressed preferably as acid value or, alternatively, as acidity calculated conventionally. This document is applicable to refined and crude vegetable or animal fats and oils, soap stock fatty acids or technical fatty acids. It does not apply to waxes. Since the methods are completely non-specific, they do not apply to differentiating between mineral acids, free fatty acids and other organic acids. The acid value, therefore, includes any mineral acids that are present. Milk and milk products (or fat coming from milk and milk products) are excluded from the Scope of this document.