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What is the Difference Between Serving Size and Portion Size?

08 May 2023

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The next time you are at the grocery store, look at the nutritional label of your favorite food and see what the serving size is. Chances are you eat more in one sitting than what is listed on the bag, box, bottle or can. Why? That is largely attributed to the difference in the serving size on the packaging and the portion size you consume at home or at a restaurant.

Serving size and portion size are often used interchangeably, but the two terms are different. To help avoid confusion and to help establish healthier eating habits, this blog will dive into why it is important to know the distinction between serving size and portion size.

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Explaining the differences between serving sizes and portion sizes

In short, a serving size is a measured amount of food or drink on a label whereas a portion size is the amount of food you eat in a single setting. You decide what a portion size is, but a serving size is decided for you by the U.S. Food and Drug Administration (FDA). 

Serving size

Many people think a serving size is a guide or recommendation on how much they should eat. However, a serving size simply represents how much a person typically eats. Some may eat more, some may eat less.

A serving size is based on the Reference Amount Customarily Consumed (RACC), a defined number by the FDA that identifies how much the average person would eat in one sitting. Serving sizes are usually represented on packaging in the following ways:

  • Mass (cups, tablespoons or teaspoons)
  • Volume (Fluid ounces for liquids)
  • Unit measurements (one slice of bread, 10 crackers, five cookies)
  • Package or container (one snack-size bag of chips)

The RAAC is beneficial for consumers because it allows you to compare two similar products. When buying packaged goods such as bread, the serving size (1 slice, for example) lets you know how the calories, fat, dietary fiber, carbohydrates, protein and added sugars stack up. If they weren’t similar, food manufacturers could deceive consumers by using smaller serving sizes to make it seem like their products have fewer calories or fat.

In 2022, the FDA updated serving size recommendations for nutrition facts labels.

Portion size

A portion describes how much food you eat at a meal. While a serving size is a predetermined amount, each individual decides what a portion size is. If the serving size is a ½ cup and you eat a cup, then 1 cup is your portion size.

There can be many servings in a single portion. For example, a heaping portion (scoop) of mashed potatoes for dinner may contain two or three servings. Likewise, a serving size for pasta varies between ½ cup and ⅔ cup, but many people eat at least a cup, which can be double the serving size.

How much you eat in a single sitting can be difficult to judge unless you plan on measuring or weighing everything – it’s easier to count chips, cookies or candy than it is to measure pasta noodles.

Here is a general guide on how to visually estimate common portion sizes:

  • 1 cup: When measuring fruits or veggies, a cup is about the size of a fist or a baseball.
  • ½ cup: When measuring grains, ½ cup roughly equals a handful or the size of a tennis ball.
  • 3 oz.: When measuring meat, 3 oz. is about the size of the palm of your hand or a deck of cards.
  • 1 tablespoon: For salad dressings, butter, cheese or other spreads, a tablespoon is about the size of your thumb. 
  • 1 teaspoon: For oils, sauces and dried herbs, a teaspoon is about the size of the tip of your pointer finger.

portion sizes graphic

Serving size examples

Many years ago, serving and portion sizes were much smaller. For example, a small bagel was 3 inches in diameter and contained 140 calories. Nowadays, you can find bagels that are 6 inches in diameter and 350 calories. A single serving of soda used to be a 12-ounce can with around 120 calories. Now, most people drink a 20-ounce bottle for their portion size, adding about 200 calories to your daily intake.

Here are some common examples of single servings:

  • 2 cups leafy greens
  • 1 slice of bread
  • 1 tortilla
  • 1 piece of fruit 
  • 1 cup milk or yogurt
  • 1 cup cut-up fruit
  • 1 cup cut-up vegetables
  • 1 cup 100% fruit juice
  • 1 cup cereal
  • 3 oz. protein (chicken, fish, pork or beef)
  • ½ cup dried fruit
  • ½ cup rice or pasta (cooked)

Why portion size and serving size matter

Large portion sizes lead to overeating, which increases your risk of many health conditions ranging from high blood pressure and diabetes to cardiovascular disease and mental health disorders.

The fast-food industry is the biggest culprit, as a portion of a burger and fries can account for more servings in one meal than you should eat in an entire day. This isn’t done on purpose, either. Many people like the value of getting more value for their money, and combination platters and dinners achieve this. By eating larger portions, not only do you consume more fat and calories, you also increase your intake of unwanted added sugars and sodium.

A serving size is 15 potato chips, but most people eat more than that. So, if you consume 30 chips and double the serving size, for example, you consume 20 grams of fat and 320 calories.

Generally, whole fruits and vegetables are among the few foods you can eat several servings of and not feel guilty. Sugars in fruit are the one exception, though. 

While they are free of added sugars, eating several servings of whole fruits can spike your blood sugar. For example, a large apple has 25 grams of sugar, with most of it coming from fructose. Eating two apples as a snack will deliver 50 grams of sugar in a short amount of time. The same goes for eating a large bowl of fruit salad – even if it’s fresh. An orange has 17 grams of sugar, a medium pear also has 17 grams of sugar, a cup of pineapple has 16 grams of sugar and a cup of grapes contains 15 grams of sugar.

What can you do to eat healthy

For starters, know how to read packages and understand food labels. You can also download healthy eating apps or visit websites like MyPlate as a guide on serving sizes.

As a general guide, fill half your plate with fruits and veggies, a quarter of your plate with protein and a quarter of your plate with carbohydrates.

Here are some additional tips to consider: 

Slow down: Every time you eat, hormones are transmitted from your brain to your stomach to indicate satiety, or the feeling or being full. It takes your brain 20 minutes to recognize if you’re full.

Don’t go too long between meals: Eating lunch at noon and not having dinner until 7 p.m. could make you overeat a larger portion size. Add a snack to your diet so you’re eating something every four hours.

Eliminate distractions: Use the dinner table for food, not to watch TV or read the news on your phone. Distractions can cause you to lose track of how much you are eating.

Avoid eating from a package: Chips, cookies and crackers are irresistible for a reason, and it’s easy to stand at the counter and snack directly from the bag. This is an easy way to lose track of portion control.

Get familiar with portion sizes: If you do not spend much time in the kitchen, take out a measuring cup, a tablespoon and a teaspoon and familiarize yourself with how much these amounts look like. It can be eye-opening how much a tablespoon of sugar is.

Use a smaller plate: Dinner plates get larger and larger these days. Use a small plate so you feel like you are eating more. No one likes an empty plate, and larger plates can make you load up your portion sizes without even thinking twice.


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