This document specifies a method for the determination of the conventional mass per volume ( litre weight in air ) of animal and vegetable fats and oils (hereinafter referred to as fats) in order to convert volume to mass or mass to volume. The procedure is applicable to fats only when they are in a liquid state. Milk and milk products (or fat coming from milk and milk products) are excluded from the scope of this document. NOTE The determination of conventional mass per volume (litre weight in air) using the oscillating U-tube method can be found in ISO 18301.