You turn over a packet to make a sensible choice. Suddenly there are percentages, serving sizes and a number that looks either reassuring or alarming. What were you trying to find out in the first place?

A useful label check begins with a question: will this work for my breakfast, packed lunch or post-workout snack? This guide is for everyday shopping. It explains how to compare products without turning every purchase into an exam.

First, find the amount the numbers describe

In the US, the Nutrition Facts panel usually gives values per labelled serving. That serving reflects an amount commonly consumed; it is not a recommendation for how much you personally should eat. If you eat two servings, the corresponding nutrient amounts double. On UK labels, the per-100 g or per-100 ml column makes comparison easier; a separate portion column may also appear. Check which column you are reading. [1] [2]

Here is an invented example, not a comparison of real brands:

B appears to provide more fibre if you compare the printed portions. A contains more fibre for the same weight. Both statements can be true. At an equal 50 g portion, A would provide 4 g and B would provide 3 g.

Neither number tells you which breakfast you will enjoy, what it costs, or what else you will eat with it. It simply answers one comparison correctly.

Pick one useful comparison

Try choosing your question before choosing your product. If you are looking for a higher-fibre breakfast, compare fibre. If you want a convenient protein-containing snack, compare protein alongside price and the amount you expect to eat. If your clinician has asked you to reduce sodium, make that your priority.

Compare foods that could reasonably do the same job. Comparing two soups for lunch is more useful than deciding whether soup or olive oil has the better numbers. They are different ingredients with different roles.

You also do not need to optimise every number at once. A product might contain more of one nutrient and less of another. Choose the trade-off that matters for this purchase, rather than searching for a packet that wins every category.

What the shortcuts mean

US percentage Daily Values are reference points, not your personalised targets: 5% or less is considered low and 20% or more high for that nutrient in a serving. Total sugars include added sugars; do not add the two lines together. [1]

On UK front-of-pack labels, traffic-light colours describe individual nutrients. A red square is not a verdict on your entire diet. Ingredients are listed in descending order by weight; specified allergens are emphasised in the ingredients list. [2]

Use these conventions in the country where they apply. An imported packet may have a different format. If you have a food allergy, follow the relevant allergen information and your care advice rather than treating this general nutrition comparison as an allergy check.

The cheapest packet is not always the cheapest useful option

Suppose one product costs £1.80 for 300 g and another £2.20 for 500 g. The first costs 60p per 100 g; the second costs 44p. Those figures are illustrative arithmetic, not current shop prices.

The larger pack costs less for the same weight, but it only suits your budget if you can afford the upfront price and use it. A small pack you finish may be more practical than a larger one you throw away. Ask how it fits the week: can you share it, freeze a suitable portion, or use it in another meal?

For an unfamiliar product, buying a small amount first is a reasonable experiment. Discovering that you dislike something after buying six packets is not a nutrition success.

Does reading labels actually change behaviour?

A 2025 Cochrane review included 25 studies of calorie labelling. Across 16 randomised studies, labelling produced a small average reduction in energy selected or purchased, with high-certainty evidence. Evidence about how much people actually consumed was less certain. Most studies concerned menus, and most were conducted in high-income countries. [3]

This is evidence for a modest effect of calorie information in the settings studied. It does not establish that scrutinising every supermarket label improves your whole diet, or that choosing fewer calories is always the appropriate goal. The review's integrated search was current to August 2021; later search results were not fully incorporated. [3]

Our practical suggestion is therefore narrower: use the label to answer a specific question, then make the purchase and move on. You do not need to become a full-time analyst of your shopping basket.

A short routine for your next shop

1. Name the job. For example, “I need a breakfast I can eat before leaving for work.”
2. Compare like with like. Use the same weight or serving amount.
3. Check the detail that matters. One relevant nutrient, ingredient or dietary requirement is a useful starting point.
4. Include real-life fit. Price, taste, preparation and storage all belong in the decision.
5. Stop when the choice is good enough. Keep a note of products you enjoy so you can buy them again without repeating the whole exercise.

If numbers make shopping stressful, simplify further: choose a familiar meal and a short list of ingredients. A label is an available tool, not a requirement to monitor everything you eat.

Turn a purchase into a meal you look forward to

Finding a useful cereal or soup is only part of the task. Think about how you will serve it, when you will eat it and whether you want it again. The next step can be as small as choosing tomorrow's breakfast tonight.

For a practical starting point, try our flexible lunch shopping list or guide to adding fibre to familiar meals. If you want help organising meals around your preferences and routine, explore WeightStart's nutrition planning and coaching options.

Sources and reading notes

This article combines official label guidance, a systematic review and clearly labelled illustrative comparisons. The examples are our practical applications, not tested interventions. Updated 2 October 2026.

1. US Food and Drug Administration. How to Understand and Use the Nutrition Facts Label. US label conventions.
2. NHS. Food labels. Reviewed 30 June 2026. UK label conventions.
3. Clarke N, Pechey E, Shemilt I, et al. Calorie (energy) labelling for changing selection and consumption of food or alcohol. Cochrane Database of Systematic Reviews. 2025;1:CD014845. doi:10.1002/14651858.CD014845.pub2. Full review. Part-funded by Wellcome; several authors disclosed involvement in included studies and were excluded from their assessment.