What Determines Serving Size? Unpacking the Science Behind Food Labels

December 19, 2025 •

4 min read

According to the U.S. Food and Drug Administration (FDA), serving sizes are based on the amount of food people typically eat, not a recommendation of how much they should eat. Understanding what determines serving size is key to accurately interpreting the nutritional information on food labels and making informed dietary choices.

Quick Summary

Serving sizes are standardized amounts set by regulatory bodies like the FDA, based on consumption data, and are used for comparing nutrition information across similar products. They differ from a personal portion size, which can vary based on individual needs.

Key Points

Serving Size is Standardized: Regulatory bodies like the FDA establish serving sizes based on national eating habit surveys, not health recommendations.
RACCs are the Foundation: Reference Amounts Customarily Consumed (RACCs) are the benchmark data used by manufacturers to set serving sizes for specific food categories.
Serving Size is NOT a Portion: A serving is a measurement on a label, while a portion is the amount you personally decide to eat, which may be more or less.
Check 'Servings Per Container': Always look at the top of the Nutrition Facts label to see how many servings are in the entire package, as many packages contain multiple servings.
Adjust Nutrients Accordingly: If you consume more than one serving, you must multiply the calories and other nutrient information to get the correct intake.
Labels Have Evolved: The FDA updated labels in 2016 with new RACCs and dual-column labels for certain package sizes to better reflect modern consumption patterns.
Your Portion is Personal: Your ideal portion size is determined by individual factors like age, gender, activity level, and specific health goals.

Who Sets the Rules for Serving Sizes?

In the United States, the Food and Drug Administration (FDA) is the primary government agency responsible for establishing and regulating serving sizes on packaged foods. The FDA mandates that serving sizes must be based on data reflecting the amounts of food and beverages people actually consume, not on what a person should consume as part of a healthy diet. This critical distinction helps consumers compare the nutritional content of similar products on a level playing field.

The Role of Reference Amounts Customarily Consumed (RACCs)

The foundation of the FDA's serving size regulations is a set of guidelines known as Reference Amounts Customarily Consumed, or RACCs. The RACCs are standardized reference amounts for over 150 food categories, based on national food consumption surveys. When a food manufacturer develops a new product, they must determine its serving size by finding the RACC that best corresponds to their product. For example, if the RACC for a certain type of pizza is 140g, the manufacturer must set the serving size as the fraction of the whole pizza that is closest to 140g.

Evolution of Serving Sizes

Serving sizes are not static; they change over time as consumer eating habits evolve. The FDA updated its serving size requirements in 2016 to reflect more current consumption patterns, based on surveys conducted in the early 2000s. This update led to some significant changes, such as the serving size for ice cream increasing from ½ cup to ⅔ cup and the serving size for soda increasing from 8 ounces to 12 ounces. For individually packaged products that are often consumed in one sitting but contain more than one RACC, the FDA introduced dual-column labeling. This shows the nutrition facts for both a single serving and the entire package, helping consumers understand the total calorie and nutrient intake if they eat the whole container.

The Difference Between Serving Size and Portion Size

This is one of the most common sources of confusion for consumers. A serving size is a standardized, regulatory-defined amount of food. A portion size, however, is the amount of food a person actually chooses to eat at one time. Your portion can be larger, smaller, or equal to the serving size listed on the package. Portion sizes are not controlled by the FDA but are influenced by a variety of personal and environmental factors.

Factors Influencing Personal Portion Size

Age and Gender: Calorie and nutrient needs vary significantly based on a person's age and gender.
Activity Level: Athletes or highly active individuals typically require larger portions to meet their energy needs.
Personal Health Goals: Individuals aiming to lose, gain, or maintain weight will adjust their portion sizes accordingly.
Environmental Cues: The size of plates, restaurant portions, and package sizes can all influence how much a person serves themselves.

Serving vs. Portion Size Comparison Table


Feature	Serving Size	Portion Size
Definition	A standardized, regulated amount of food.	The actual amount of food a person eats.
Determined By	Regulatory agencies (e.g., FDA) using consumption data (RACCs).	Personal appetite, hunger, dietary needs, and environmental factors.
Listed On	The Nutrition Facts label on food packaging.	Not listed; determined by the individual at mealtime.
Purpose	To provide a consistent basis for comparing the nutritional value of products.	To meet an individual's specific hunger and energy needs at a given time.
Can It Change?	Only through government updates based on national surveys.	Varies from day to day and meal to meal for each person.

How to Use Serving Size Information Effectively

Reading the nutrition facts label effectively begins with understanding the serving size. Always check the number of servings per container, as a single package may contain multiple servings. If you consume more than one serving, you must adjust the nutritional values accordingly. For example, if a bag of chips has two servings, and you eat the entire bag, you must double all the calories, fat, sodium, and other nutrients listed on the label. This mindful approach allows you to accurately track your intake.

For more detailed information on reading and understanding the nutrition facts label, the official FDA website is an excellent resource: How to Understand and Use the Nutrition Facts Label.

Conclusion

Serving size is a regulated, standardized measurement designed to provide consumers with consistent information for comparing food products. It is not a dietary recommendation but a reflection of typical consumption patterns based on extensive data. In contrast, portion size is the amount an individual chooses to eat, a decision influenced by personal hunger, health goals, and environmental factors. By understanding this difference and correctly interpreting the information on a food label, consumers can make more informed choices and align their eating habits with their personal dietary needs. Paying attention to both the official serving size and your personal portion is a powerful tool for maintaining a healthy and balanced diet.

Frequently Asked Questions

No, a serving size is not a recommendation for how much you should eat. It is a standardized amount, set by agencies like the FDA, that reflects the quantity people typically consume. This allows for fair comparisons of nutritional information between similar products.

A serving size is a regulated, uniform amount listed on a food label, while a portion size is the amount of food an individual chooses to eat at one time. Your portion size can differ from the manufacturer's suggested serving size.

In the United States, the Food and Drug Administration (FDA) is responsible for determining and regulating the serving sizes on most packaged foods. They base these sizes on consumer consumption data from national surveys.

Serving sizes were updated by the FDA in 2016 to reflect more current consumption habits. For example, the serving size for ice cream increased from ½ cup to ⅔ cup because survey data showed people were eating larger amounts.

RACCs, or Reference Amounts Customarily Consumed, are the benchmark amounts of food used by the FDA to determine serving sizes. Food manufacturers use the appropriate RACC for their product category to set a realistic serving size for their label.

Dual-column labels are required on some packages that contain between two and three servings, but could be eaten in one sitting. They list nutritional information for both a single serving and the entire package, making it easier for consumers to understand the total nutrients if they eat it all.

You can learn to estimate your own portions by using household items or your hand as a guide. For example, a serving of meat is about the size of your palm, and a serving of vegetables is about the size of your fist. Paying attention to your body's hunger and fullness cues is also key.