A serving size or portion size is the amount of a food or drink that is generally served.
A distinction is made between a portion size as determined by an external agent, such as a food manufacturer, chef, or restaurant, and a "self selected portion size" in which an individual has control over the portion in a meal or snack.[1] Self-selected portion size is determined by several factors such as the palatability of a food and the extent to which it is expected to reduce hunger and to generate fullness.