Check the comparison basis first
A table may give information per 100 g, per 100 ml or per serving. In the EU, values per 100 g or ml help comparisons; the US format explained by FDA starts with a serving. Always read the heading and the number of servings in the package.
A repeatable calculation
Illustrative example: a product with 180 kcal per 100 g provides 270 kcal in 150 g. The same multiplier, 1.5, applies to protein, fat and other values. If the label describes the prepared product, check that its preparation matches yours before using those numbers.
Look beyond calories
Compare fibre, salt or sodium, saturated fat and ingredients as relevant to your choice. A percentage daily value is a general reference in that labelling system, not a measurement of your personal requirement. Rules and reference values differ between countries, so do not assume every label uses the same framework.
A sequence for shopping
For two similar products: check units, compare the same amount, read the ingredients and consider the portion you will use. One isolated number does not describe your whole diet. If you have allergies, always check the specific package information; comparing nutrients is not an allergen safety check.
