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How to read a nutrition label
The table on the back of a package is the most precise calorie source you have for everyday food. You only need to know where to look – and where manufacturers leave room for misunderstanding.
In short
- In the EU, energy and nutrients must be given per 100 g or 100 ml.
- 'Per portion' is voluntary – check how many grams the portion is.
- 1 kcal = 4.184 kJ; log kcal in your diary.
- Check calories yourself: fat × 9, carbohydrate × 4, protein × 4, fibre × 2.
What must be on the label
In the European Union, nutrition labelling is set by Regulation (EU) No 1169/2011. The mandatory table has seven items: energy, fat, of which saturates, carbohydrate, of which sugars, protein and salt. Fibre and other nutrients may be added voluntarily.
Importantly, these values must be given per 100 g or per 100 ml. That lets you compare products regardless of pack size.
Per 100 g vs per portion
A manufacturer may add a "per portion" column – but must state how much the portion weighs and how many portions are in the pack. This is where most errors happen:
- The manufacturer's portion may not be yours. A "30 g serving" of muesli is less than many people actually pour.
- For drinks and sweets the portion is often small, so the number looks harmless.
- The most reliable approach: log using the per 100 g value and enter the weight you actually ate.
Where the calories come from
The energy value on the label is not measured by burning the food – it is calculated from the nutrient content using fixed factors set by the same regulation:
- fat: 9 kcal/g
- carbohydrate and protein: 4 kcal/g
- alcohol: 7 kcal/g
- fibre: 2 kcal/g
- polyols (e.g. some sweeteners): 2.4 kcal/g
| Nutrient | Amount | × factor | kcal |
|---|---|---|---|
| Fat | 10 g | 9 | 90 |
| Carbohydrate | 60 g | 4 | 240 |
| Fibre | 8 g | 2 | 16 |
| Protein | 10 g | 4 | 40 |
| Energy | 386 |
If your result roughly matches the number on the pack, you have read the label correctly; small differences come from rounding. As for units: 1 kcal = 4.184 kJ, so the label shows a higher number in kJ and a lower one in kcal. Always log kcal.
Logging a package in your diary
- Scan the barcode. It is the fastest option, but the database may not know your version of the product – recipes change and some products differ between countries.
- Compare with the package. If the per-100 g values differ, the package in your hand wins. If the product is missing, photograph the nutrition table.
- Enter the real amount. Whole pack, half, or number of pieces – not the manufacturer's portion if you ate a different amount.
- Save the product. Next time you buy it, logging takes one tap.
Frequently asked questions
Why are calories on labels given per 100 g?
In the EU, Regulation 1169/2011 requires it so that products can be compared. Per-portion values are a voluntary addition.
What is the difference between kJ and kcal?
They are two units of energy: 1 kcal = 4.184 kJ, so the kJ number is always about four times higher. Log kcal in your diary.
What if the scanned value differs from the package?
The package you have is what counts. Recipes change and product versions differ by country, so always check scanned values.
Sources
This guide is general information for healthy adults, not medical advice. If you are pregnant, breastfeeding, have or have had an eating disorder, or need a therapeutic diet, talk to a doctor or registered dietitian.