Learn the fluid ounces-to-liters conversion rate, which is 1 fl. oz. to 0.0295735296 liters. Multiply your fluid ounces by 0.0295735296 to convert the ounces to metric units. You can set up the equation as: y * 0.0295735296 = z.where y is the amount of fluid ounces you wish to convert. For example, 100 fl. oz. is 100 * 0.0295735296, which equals 2.95735296 liters.ass and volume measurements of ounces are not related. A fluid ounce of a liquid, for example, may weigh more or less than a ounce in weight. To convert a mass ounce to the metric system, you must express the weight in terms of grams.