How is a serving size calculated? Decoding FDA Regulations

November 28, 2025 •

2 min read

According to the FDA, serving sizes on food labels are based on the amount of food people typically eat, not the amount they should eat. This critical distinction explains how is a serving size calculated based on consumer habits, not dietary recommendations. Food manufacturers follow strict guidelines to determine this standardized amount.

Quick Summary

The FDA determines standardized serving sizes using Reference Amounts Customarily Consumed (RACC), which reflect typical consumption patterns. Calculation methods vary depending on whether the product is discrete, divided, or sold in bulk quantities.

Key Points

FDA's RACC system: The FDA uses Reference Amounts Customarily Consumed (RACC), derived from consumption surveys, as the basis for calculating serving sizes for different food categories.
Serving vs. portion: Serving size is a standardized unit on the label, while portion size is the amount an individual chooses to eat, which may be more or less than a serving.
Discrete unit calculation: For items like cookies or crackers, the serving size is the number of units that is closest to the RACC by weight.
Divided products calculation: For foods like pies or pizzas, the serving size is a fractional slice based on the product's total weight relative to the RACC.
Bulk product calculation: For goods like yogurt or cereal, the serving size is the common household measure (e.g., cup) that best approximates the RACC weight.
Dual-column labels: Some large packages that may be consumed in one sitting feature dual-column labels showing nutrition info per serving and per package.

The Foundation: Reference Amounts Customarily Consumed (RACCs)

At the core of how a serving size is calculated in the U.S. is the Reference Amount Customarily Consumed (RACC). The FDA establishes these standardized amounts based on nationwide food consumption surveys conducted by the USDA. It is a reference amount for a given category of food, reflecting what people typically eat in one sitting.

The manufacturer translates the RACC into a practical household measure (e.g., cup, piece, slice) and a metric weight (grams). The calculation process depends on the product's format: discrete units, divided products, or bulk goods.

Calculation Methods for Different Product Types

1. Discrete Units

For individually packaged items like cookies, the serving size is the number of units closest to the RACC by weight. For example, if the RACC for cookies is 30 grams and one cookie weighs 10 grams, the serving size is 3 cookies. If a single unit weighs between 67% and 200% of the RACC, the serving size is one unit.

2. Divided Products

For items like pies that are typically divided, the serving size is a fractional slice. It's calculated by dividing the RACC (e.g., 125 grams for pie) by the total product weight (e.g., 500 grams), resulting in a serving size like ¼ slice.

3. Bulk Products

For bulk items such as yogurt or cereal, the serving size is the household measure (like a cup) that is closest to the RACC by weight. For instance, if the RACC for yogurt is 170 grams and one cup weighs 340 grams, the serving size would be ½ cup (170g).

A Crucial Distinction: Serving Size vs. Portion Size

Understanding the difference between serving size and portion size is vital for informed dietary choices.


Feature	Serving Size	Portion Size
Defined by	U.S. Food and Drug Administration (FDA)	The individual consumer
Reflects	What people typically eat	How much food you choose to eat at one time
Location	On the Nutrition Facts label	On your plate, based on your hunger
Comparability	Standardized to allow for comparison between similar products	Varies depending on age, gender, appetite, and other factors
Example	The label says '1 cup (245g)' of soup	Eating the entire 15-ounce can of soup

The Rise of Dual-Column Labeling

Certain packages containing between 200% and 300% of the RACC may feature dual-column labels. This provides nutritional information for both a single serving and the entire package, helping consumers easily understand total calories and nutrients if they consume the whole container.

Conclusion

Understanding how a serving size is calculated empowers consumers to make better food choices and interpret nutrition labels accurately. The FDA's RACC-based system provides a standardized benchmark based on typical consumption. While serving size isn't a strict dietary rule, it's a helpful tool for portion control and managing nutrient intake. For more on FDA labeling changes, consult the official FDA guidance.

Frequently Asked Questions

A serving size is a standard, regulatory-defined amount of food shown on a nutrition label, based on what people typically eat. A portion size is the amount of food an individual chooses to eat at one time, which can differ from the serving size.

Food manufacturers are responsible for calculating and determining the serving size for their products, but they must do so according to the standardized guidelines and Reference Amounts Customarily Consumed (RACCs) set by the FDA.

RACC stands for Reference Amount Customarily Consumed. It's a standardized reference amount for a food category, based on consumer surveys, that serves as the foundation for setting the serving size on a Nutrition Facts label. It ensures consistency across similar products.

The FDA updated serving sizes to reflect modern consumption habits, which have changed since the previous guidelines were set. For example, the RACC for ice cream changed from 1/2 cup to 2/3 cup to align with how much people actually eat.

For packages with 200%-300% of the RACC that could be consumed in one sitting, manufacturers must provide dual-column labels. One column shows the nutrition facts for a single serving, and the second column shows the facts for the entire package.

A 20-ounce soda bottle, previously considered multiple servings, is now labeled as a single serving because people typically drink it all at once. For larger containers, dual-column labels might be used.

By knowing the standard serving size, you can accurately track your nutrient and calorie intake. If your portion is larger or smaller, you can adjust the nutritional values accordingly to make informed decisions about your diet.