Understanding serving sizes and ingredient amounts

Serving size is the least glamorous line on a label and the one that keeps the other lines honest. Skip it, and a comparison between two products is mostly guesswork.

Where the serving size is printed

On a Nutrition Facts or Supplement Facts panel, the serving size sits near the top. It may be a household measure (one cup, two capsules, one tablespoon) and sometimes a weight as well. The servings-per-container line tells you how many of those servings the package holds. A bottle of 60 capsules with a serving of 2 capsules contains 30 servings, not 60.

Per serving and per container

The ingredient amounts listed under the serving size apply to one serving unless the label clearly marks another column. Some newer food labels also show amounts per package when a person might eat the package in one sitting. Read the column headings before you read the numbers.

Units that are easy to mix up

• Milligrams (mg) and micrograms (mcg or µg) differ by a factor of one thousand.
• An amount of a compound and an amount of an elemental mineral can share an ingredient name and still be different figures.
• Percent daily value is a comparison with a reference amount, not a score out of 100 for product quality.
• A “proprietary blend” may list ingredients without giving each one its own amount.

A simple way to compare two labels

Write down four things for each product: the serving size, the servings in the package, the ingredient you care about, and the amount of that ingredient per serving, including the unit. If one serving is one capsule and the other is three, the raw numbers are not ready to compare until you account for that. This exercise shows you what the label says. It does not tell you which product you should take.

What the number leaves out

An amount per serving does not describe quality, absorption, or whether the ingredient belongs in your diet. It is still the right first check. A product you cannot compare on the label is a product you cannot compare at all.