Convert nutrition between serving sizes.
Every nutrient on a label scales linearly with weight, so one ratio converts all of them: the portion weight divided by the label serving weight. That single scale factor multiplies calories, protein and everything else. The per-100-gram figure is included because it is the region-neutral basis that lets you compare products whose declared serving sizes differ.
Linear serving conversion
Scale = portion grams / label serving grams; portion nutrient = label nutrient x scale; per 100 g = label nutrient / label grams x 100
These figures are population-average estimates for general planning only and are not medical or dietetic advice. Individual energy and nutrient needs vary widely with body composition, activity, medication and health status. Consult a qualified health professional or registered dietitian before making significant changes to what you eat, and especially if you are pregnant or breastfeeding, are under 18, or have a medical condition or a history of disordered eating.
Yes. Multiply any per-serving figure — fat, sodium, sugar, a vitamin in micrograms — by the same scale factor. The relationship is strictly proportional to weight.
Use millilitres in both fields and the ratio still holds. Only mix units if you know the density, since 100 ml of oil weighs about 92 g while 100 ml of syrup weighs closer to 130 g.
It is mandatory on EU and UK labels and it is the only basis on which two products with different serving sizes can be compared directly. A cereal declaring 30 g servings and one declaring 45 g look very different per serving but are directly comparable per 100 g.