Serving Size vs. Portion Size: Which is Which?

Having diabetes is hard work, especially when it comes to meal planning. In fact, many people with diabetes find meal planning to be the most challenging aspect of having diabetes. There’s so much to think about: carbohydrate, timing of meals, reading food labels, controlling portions… Speaking of food labels and portions, have you ever stopped to think about the difference between a serving size and a portion size? Well, they’re the same thing, right? Sorry, but that’s wrong. It’s important to know the difference between the two, not only for blood glucose control but for weight control as well. Let’s take a closer look.


Consider the term “serving size.” Where do you usually find these words? On a Nutrition Facts label (otherwise known as a food label). In the United States, we’re fortunate to have the nutrition information about a particular food listed on the package or container. Although it can be confusing and time-consuming to read food labels, once you know what to look for, you can breeze through a label in no time. The “serving size” on a food label refers to the amount of that food usually eaten at one time, according to the United States Department of Agriculture (USDA).

What determines serving sizes? Well, the data comes from nationwide food consumption surveys. Foods that are measured in bulk, such as cereal or flour, are typically listed in common household terms, such as cups, tablespoons, teaspoons, or fluid ounces. Foods that are divided up to serve more than one person, such as pizza or cake, are listed in a fractional amount, such as 1/4 pizza or 1/12 cake. Serving sizes for foods that come in “discrete units,” such as bread or cookies, are usually listed as “1 cookie (30 grams)” or “2 slices bread (50 grams).”

No doubt you’ve read a label and shook your head thinking, “There’s no way that just one cookie is a serving size,” or “Who eats just 1/2 a cup of ice cream?” While these serving sizes can certainly seem unrealistic, it’s very important that you always look at the serving size on a Nutrition Facts label because all of the nutrients listed on that label, such as fat, carbohydrate, and sodium, are based on the serving size. If you end up eating twice or three times as much as the serving size, the amount of carbohydrate (along with calories and fat) will double or triple, thereby affecting your blood glucose levels and possibly your weight, too.

You should think about something else when it comes to serving size: If you use the Food Pyramid, food lists, or exchange lists for carbohydrate counting, for example, a “starch exchange” or a “carb serving” is a particular amount of food that provides about the same number of calories and carbohydrate as another, similar food. For example, a 1-ounce slice of bread contains about 80 calories and 15 grams of carbohydrate, the same as in 1/3 cup of cooked pasta. But the serving size on a box of pasta is two ounces (dry). Cooked, those two ounces of pasta yield 1 cup, which contains roughly 45 grams of carbohydrate. Tricky, isn’t it?

A good piece of advice is to always go by what’s listed on the food label, if it’s available, rather than on a food list. And if the food doesn’t have a food label, consider purchasing a good food counts book to look up the grams of carbohydrate. One popular choice is The Doctor’s Pocket Calorie, Fat & Carbohydrate Counter, although there are many other good food counts books available, as well.

So, what’s the difference between serving size and portion size? A serving size is a unit of measure that describes a recommended amount of a certain food. A portion size, on the other hand, is the amount of a food that you choose to eat. For example, a serving size of Fritos corn chips is 1 ounce, or 32 chips. Your portion size, however, might be more like 3 ounces (similar to three handfuls), or close to 100 chips. Portion sizes aren’t necessarily always larger than serving sizes. You might eat only 15 Fritos, and that would be your portion size.

If you tend to do a lot of reading or surfing on the Internet, be careful: Some articles, books, and Web sites use the terms “serving size” and “portion size” interchangeably. They’re not the same.

The moral of the story, then, is always to look at the serving size, whether on a food label or in a food counts book, when meal planning. Doing so will help you mange your diabetes and your weight.

Next week: More on portion control!

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  • dmoltzan

    Although you have explained these two terms, it does not simplify eating proper amounts of foods for weight and diabetes; a testimonial to how confusing the food industry has made understanding healthy eating.

    When an entire steak, a bowl full of pasta and meatballs, or several teaspoons of oil or butter per meal no longer becomes a paradigm for a serving size, we will have progressed.

    The obesity epidemic is a symptom of failure on our industry’s part to teach proper nutrtion needs of people, young or old.

  • Confused82

    I’ve made a Tuna Helper and Hamburger Helper as directed on the box. The box says serving size is 1 cup and the box contains 5 servings/cups.

    But measured after cooked, three different times, with three different flavors, it came out as only four cups prepared.

    My question is how to count the carbs? If it says there are 30g per cup and it only makes 4 cups, is it really 30g? Or is it 150g per package and 37.5g per cup/serving?

  • acampbell

    Hi Confused82,

    That’s very interesting. My question to you is: did you make the Hamburger Helper exactly according to directions? I’m sure you did, but if you didn’t add enough water, for example, that could certainly affect the amount of the final product. I think your best bet is to contact General Mills, the makers of Hamburger Helper. They have a consumer phone number, which is 1-800-248-7310, and should be able to explain the discrepancy. Please let us know what you find out!

  • jenny

    Very good information. keep it up.

  • fatemeh

    Thank you so much.very helpful

  • Babi Dan

    Thank you very much for helping me distinguish between portion size and serving size. But then how am I going to be able to translate calculations of diabetic foods such as breakfast: millet porridge served with roasted ground nut together with a glass of mixed juices made from passion fruits, water melon and beetroot; Lunch: boiled fresh fish served with brown rice and yams together with avocado and supper: bean stew served with whole grain posho together with vegetable salads in terms of 50% carbohydrate, 20% protein and 30% fats

  • acampbell

    Hi Babi,

    Is this the dietary prescription that was recommended for you? Ideally, you should meet with a dietitian who can help break this down for you in terms of how much to eat from each food group. You can look up the nutrient values of the foods you eat using a food counts book or a Web site such as But in order to determine the right balance of foods, you would need a meal plan calculated for you based on your weight and activity level. That’s where a dietitian comes in. Your doctor can give you a referral to one who is in your community.