Determining serving size on your nutrition fact label is a question that comes up occasionally, and seems very simple on the surface. However, there is an FDA chart on displaying the proper serving size for your food, which may or may not simplify things, as well as the general FDA guidance on nutrition labeling and serving sizes.

You should certainly refer to those documents for a deeper understanding of serving sizes, as there's no way we can cover all the nuances in this blog post. Still, we'll try to distill all that documentation into an easy to follow step-by-step guide for determining your serving size.

Keep it Simple - Use Your Judgment

First things first - don't overthink it. If you make cookies, a serving is probably one cookie. If you make soup or a beverage, a serving is probably one cup.

The FDA Rules and How to Use Them

The way the FDA decided on their serving sizes is as follows:

The FDA calculated the reference amounts ... to reflect the amount of food customarily consumed per eating occasion.

This makes good sense. They put food in front of lots of different people, see how much they consume, and then use that measurement as a standard for food companies to use on their labels.

So how to use the rules?

1. Go to the FDA RACCs table (and here's the set of serving sizes for the old nutrition label format) to find your food product category.
2. Note the reference amount (usually in grams) and household measure (e.g. cup(s), piece(s)) for your product's category.
3. Calculate the fraction of your package (or number of discrete units in the package) that is closest to the reference amount.
4. Use that fraction (or whole number, if your package has discrete units) as your serving size.

A Concrete Example

To provide an example to go along with the steps above, say we make cookies. Each package has 10 cookies and the entire package is 400 grams, meaning each cookie is 40 grams on average. We look at the FDA table, find cookies, and see that the reference amount is 30 grams and the household measure is "pieces". Each of our cookies weight 40 grams on average, so 1 cookie is the closest to the reference amount of 30 grams.

Thus, our serving size should be listed as "1 cookie (40 grams)" or "1 piece (40 grams)".

If our average cookie is 60 grams, we show it as "1/2 cookie (30 grams)". And if an average cookie is 10 grams, we list it as "3 cookies (30 grams)".

Gaming the Rules

A lot of companies game the system and actually use the FDA guidelines to their advantage. What the FDA didn't account for in determining their reference amounts is the fact that consumer behavior changes depending on what you put in front of them. If you fill a cup half way, then I'll drink half a cup. If you fill it all the way, I'll drink all of it.

For example, when someone buys a drink at a store they probably intend to drink the whole drink. They look at the nutrition facts and everything looks OK. What they may not realize is that the drink they think is just 1 serving might actually be 2.5 servings.

So, it's a tricky game following the FDA rules. On one hand you want to be as clear as possible with your customers, and on the other hand you want to follow the rules. In a strange way, following the FDA rules allows you to mislead your customers while technically going by the book.

Apologies for the rant! Back to our regularly scheduled programming...

Edit (April 3, 2014): The FDA is proposing to update the serving size rules to remove this "gaming" of the rules. We think that's great.

Key Takeaways

The key concept here is pretty simple. Use your judgment and think about how much of your product is usually consumed in one sitting - that's your serving size. If you are confused or want more guidance, find your food product category in the FDA table. If it's not there, you can go back and use your judgment or contact the FDA to explain your product and situation - they'll hopefully provide guidance in a timely manner.