The Difference Between ‘Portion Size’ and ‘Serving Size’ (and Why It Matters)

Have you ever been enjoying a sleeve of Oreos when someone decides to chime in with the fact that, actually, a serving size is only three cookies? We hear about “serving sizes,” “portions” and often “portion control” all the time, but what do they actually mean? Is there a meaningful difference, or do they all end up making you feel weird about how many cookies you just ate?

If you’re confused, you’re not alone. A new consumer survey* from the International Food Information Council (IFIC) reports that while nearly half (48%) of participants correctly defined “serving size,” that same percentage “incorrectly associates the definition for portion size with that of serving size.” Here’s the difference between serving and portion sizes, and what it means for your health goals.

Serving sizes: What’s on the label

Serving sizes are the standardised amount of food that you see at the top of the Nutrition Facts labels. One package of food can (and often does) contain multiple servings, and a serving size is not meant to tell you how much you should eat in one sitting. In fact, the The FDA explicitly states that “by law, serving sizes must be based on the amount of food people typically consume, rather than how much they should consume.”

In 2016, the FDA made changes to many Nutrition Facts labels so that when people look at calories and nutrients on the label, the serving sizes more closely match what they are consuming. For instance, the serving size for ice cream had long been listed at half of a cup, but is now the much more realistic two-thirds of a cup. But does this mean that two-thirds of a cup of ice cream is how much you “should” be eating? Not quite.

Portion sizes: How much you actually eat

A portion size is simply how much food you eat in one sitting. How much you eat depends on personal preference and dietary needs — not what the label says to eat.

Some reasons you might want to understand your portion sizes include hitting your nutritional requirements, avoiding food waste, and feeling comfortably satiated when you eat.

Why it matters

The IFIC survey found that although serving sizes are not designed to be recommendations for how much to eat, many consumers still use them for that purpose. Likewise, Dr. Ali Webster says in Healthline that “it seems that many people have internalized that information as a recommendation for how much to eat when that’s not necessarily the case.”

It’s true that understanding serving sizes helps you make sense of food labels, so that you can get a more accurate sense of the nutritional makeup of your food depending on how many servings you eat. Your portions, however, can be much larger or smaller than the serving size for any number of reasons.

Here’s one way the difference between serving size and portion size might come into play: A serving size of grapes is half of a cup (around 16 grapes). If you grab about two handfuls, however, your portion size might be a full cup–two servings. Knowing your personal portion size would be necessary to count calories, track macros, or report to your physician how much fruit you typically get in your diet.

The bottom line

While something’s serving size is going to be the same for everyone looking at the Nutrition Facts label, the portion size depends on your body and your needs. Use serving sizes to understand the nutritional facts about the food. Then, your portion size should be dictated by personal factors like hunger cues and health goals. In short: Serving sizes are mass produced; portion sizes are individual.

*The survey uses data from interviews with 1,000 adults, ages 18 and up, conducted in Nov. 2021 and was published January 2022.