The Food and Drug Administration determines how serving sizes are represented on food labels. They must be in household or metric terms. Serving sizes may be considered the most important aspect of the food label, because the label's representations of all its nutrients are based on a serving.

The FDA allows the use of common household measures on food labels, which include: table or teaspoons, a piece, a slice, a cup, a fractional amount, and other common household containers. Ounces are only allowed if another option isn't reasonable and if a visual comparison of the unit is provided. As for metrics, the units that are allowed are grams and milligrams.

Learn more about portion control