This international standard specifies a method for the In Vitro determination of Sun Protection Factor (SPF). This method is applicable to sunscreen products in form of an emulsion or hydroalcoholic onephase formulation, excluding in form of a lose or compressed powder or stick. Specifications are given to enable determination of the spectral absorbance characteristics of SPF protection in a reproducible manner. Use of this method is strictly for the determination of a static Sun Protection Factor. It is not validated for the determination of water-resistance properties of a sun-protection product.