One Label, Three Portions: A Serving-Size Audit

Start at the top of the label

On the FDA’s teaching label, one cup of lasagna is one serving. The label lists 280 kcal and 850 mg sodium per serving. The portion is an amount people typically consume, not a recommendation to eat that amount. If your portion is larger or smaller, the displayed nutrient values need to be scaled.

Our Nutrition Label Decoder does this arithmetic locally in your browser. The original package remains the source of the values; the calculator does not identify the product or test its composition.

Do the multiplication before interpreting the number

For 1.5 cups, the arithmetic is 280 × 1.5 = 420 kcal and 850 × 1.5 = 1,275 mg sodium. The displayed 37% Daily Value becomes approximately 55.5% before normal label rounding. These are calculations from the FDA’s example label, not a test of a Nutrinaut meal scan or a recommendation for an individual diet.

Three common mistakes

1. Using per-container as per-serving: check how many servings the package declares.
2. Adding added sugar to total sugar: on a US label, added sugar is included within total sugar, not an extra amount.
3. Mixing reference systems: US %DV and EU or UK %RI use different labelling frameworks. Keep the country and unit with the number.

Percent reference values provide context for a general population label; they are not personalised limits. For a prescribed diet, rely on your clinician’s instructions and the actual package information.

Repeat this audit on a real package

Write down the package’s country, serving size, servings per container and the exact units shown. Measure or estimate the amount actually eaten, divide that amount by the label serving size, and multiply each value by the resulting serving count. If any ingredient or recipe value is unknown, leave it unknown rather than letting a calculator invent it.

Open the label decoder or read the full label guide.