ISO 3961:2013 specifies a reference method for the determination of the iodine value (commonly known in the industry as IV) of animal and vegetable fats and oils, hereinafter referred to as fats.
An annex describes a method for the calculation of the IV from fatty acid compositional data. This method is not applicable to fish oils. Furthermore cold-pressed, crude and unrefined vegetable oils as well as (partially) hydrogenated oils can give different results by the two methods. The calculated IV is affected by impurities and thermal degradation products.