How to compare two snack labels fairly

A fair snack-label comparison starts with one decision, use the same unit on both packs. If you switch between per serving on one label and per 100g on the other, you can make almost any product look lighter or heavier than it really is. The NHS guidance on reading food labels is clear on this point, a portion and 100g are different comparison bases, and you should compare like with like.

For many day to day choices, especially when you are comparing two products side by side on a shelf or on your kitchen table, per 100g is the simplest starting point. It strips out brand-chosen serving sizes and lets you compare the nutrition table on equal terms. If you want a refresher on when each basis is useful, our guide to comparing labels per 100g and per serving covers the basics. Here, we will use a worked task instead of a shopping list, so you can see how to compare two snack labels fairly in practice.

Start by choosing one comparison basis

When people say they are comparing two snack labels on the same weight basis, what they usually mean is this, both products need to be measured in the same units before any judgement is made. In UK nutrition labelling, the two bases you will usually see are per 100g and per serving.

Per 100g is often more useful when:

• the products are similar foods, such as two cereal bars, two nut mixes, or two bags of popcorn
• the serving sizes are different or vague
• one brand uses a small serving to make the front of pack numbers look lower
• you want the cleanest comparison of the nutrition table

The NHS specifically advises using the nutrition information to compare foods, and notes that a portion and 100g are not the same basis, so care is needed when comparing labels (NHS food labels guidance).

Per serving can still be useful, but only after you know what the serving actually is. If a whole pack is commonly eaten at once, per pack may also matter in real life. The problem is that serving sizes are set by the manufacturer, so they are not a neutral unit. Two similar snacks can look different simply because one company calls 25g a serving and the other calls 40g a serving.

If you want a broader refresher on where to find each part of the table and what the main terms mean, see our guide to understanding food labels. We are not repeating that guide here. We are using it.

A worked example with two same-weight packs

Let us compare two imaginary same-weight snack packs, each weighing 40g. We are not reviewing products, only showing the task.

Because both packs weigh the same, you can compare:

• per pack, because each whole pack is 40g
• per serving, if the serving is the whole pack
• per 100g, because that remains the standard basis

That makes this the easiest kind of label comparison.

Imagine the back-of-pack tables show this:

Snack A, per 100g:

• Energy 500 kcal
• Fat 28g
• Saturates 3.0g
• Sugars 18g
• Salt 0.90g
• Fibre 6g

Snack B, per 100g:

• Energy 460 kcal
• Fat 19g
• Saturates 2.2g
• Sugars 24g
• Salt 0.30g
• Fibre 8g

Because both packs are 40g, you can also work out the per pack amounts by multiplying each per 100g figure by 0.4.

Snack A, per 40g pack:

• Energy 200 kcal
• Fat 11.2g
• Saturates 1.2g
• Sugars 7.2g
• Salt 0.36g
• Fibre 2.4g

Snack B, per 40g pack:

• Energy 184 kcal
• Fat 7.6g
• Saturates 0.88g
• Sugars 9.6g
• Salt 0.12g
• Fibre 3.2g

Now the comparison is straightforward.

Energy Snack B is lower in energy on both bases, because the packs weigh the same and the per 100g figure is lower. There is no contradiction to resolve.

Fat Snack A is higher in total fat. That does not tell you whether it is automatically the better or worse choice overall. It only tells you that, gram for gram and pack for pack, it contains more fat.

Saturates Snack A is also higher in saturates. This matters because saturates are listed separately from total fat for a reason. If you are comparing two similar snacks, a lower saturates figure may be one useful point of difference.

Sugars Snack B is higher in sugars. Again, this is a comparison point, not a verdict on the whole food. A higher sugars figure might come with other differences in ingredients or fibre, which is why reading only one line of the table can mislead.

Salt Snack A is higher in salt. On a same-weight comparison, this is easy to see and easy to trust.

Fibre Snack B is higher in fibre. That is useful because fibre is often not obvious from the front of pack. If fibre matters to you when choosing everyday snacks, the back table may tell you more than the headline claims on the front. We have a separate guide on how fibre claims differ on labels, which is useful when the pack says “source of fibre” or “high fibre” but you want to know what that claim is and is not saying.

The key point is that none of this required guesswork. We did not need to decide whether one pack was a better snack in every sense. We only needed to compare the same nutrients on the same weight basis.

This is also where people can over-read the numbers. If Snack A is lower in sugars but higher in salt and saturates, and Snack B is lower in salt and saturates but higher in sugars, the label does not produce one universal winner. It answers narrower questions. Which has more sugar, more salt, more fibre, more energy, on the same basis? That is the proper job of the table.

What changes when the serving sizes differ

The comparison gets harder when the pack sizes or serving sizes differ, or when brands present different serving assumptions.

Imagine two snack packs that look broadly similar from the front. One says:

• 95 kcal per serving
• serving size 20g

The other says:

• 110 kcal per serving
• serving size 30g

At a glance, the first one can look lighter. But the serving is much smaller. If you stop there, you are not comparing like with like.

This is exactly why per 100g is often the safer starting point. If the back tables show:

Snack C, per 100g:

• Energy 475 kcal
• Fat 22g
• Saturates 2.5g
• Sugars 16g
• Salt 0.50g
• Fibre 7g

Snack D, per 100g:

• Energy 367 kcal
• Fat 14g
• Saturates 1.1g
• Sugars 12g
• Salt 0.45g
• Fibre 6g

Then Snack D is lower in energy per 100g, even though its quoted per serving energy looked higher on the front. The front number was shaped by a larger serving.

There are two practical ways to handle this.

First, return to per 100g. This is usually the quickest and cleanest method.

Second, recalculate both products to the same real-world amount. For example, if you know you usually eat 30g, convert both labels to 30g. To do that from per 100g, multiply by 0.3. To convert a 20g serving to 30g, multiply by 1.5.

That sounds fiddly, but the logic is simple. If one snack gives 95 kcal for 20g, then 30g would be 142.5 kcal. Suddenly the “lower calorie per serving” product no longer looks lower when you compare the same amount eaten.

This is why we are careful about comparing two snack labels on the same weight basis rather than accepting the serving line at face value. Serving sizes can be useful, but they are not neutral. They describe a chosen portion, not a fixed law of nature.

There is also a UK context point here. Labels sold in Great Britain commonly provide mandatory nutrition information in a set format, including values per 100g or per 100ml. Additional per serving information may be given, but it sits alongside the standard basis rather than replacing it. If you are reading articles from outside the UK, or looking at imported products, presentation can vary, so it is worth checking which rules actually apply to the pack in your hand.

Check the parts of the label that numbers do not settle

A fair comparison is not only about the nutrition table. Some important questions are answered elsewhere on the pack.

Ingredients order Ingredients are listed in descending order by weight at the time of manufacture. That means the first few ingredients usually tell you more about what the product mainly consists of than a front-of-pack slogan does. If one snack starts with oats and nuts and another starts with sugar and glucose syrup, that is a factual difference in composition. It does not tell you everything about the finished product, but it is relevant.

Allergen information For anyone managing an allergy or intolerance, the ingredients list and allergen emphasis are not optional extras. The Food Standards Agency guidance for consumers explains the importance of checking ingredient and allergen information carefully. A nutrition table cannot tell you whether a food is suitable for a particular person with an allergy. We do not infer personal suitability from a general label, and readers should check the actual pack each time.

Claims such as no added sugar A claim like no added sugar answers a different question from the total sugars line in the nutrition table. It means sugars have not been added as ingredients in the way covered by the claim rules, but it does not mean the product is sugar-free or low in sugar. Dried fruit, fruit purée, or fruit juice ingredients can still contribute sugars naturally present in the product. That is why it is worth reading both the claim and the table, not one instead of the other. Our explainer on what no added sugar and low sugar claims mean on labels goes into that distinction in more detail.

Storage and handling This is not usually part of a nutrition comparison, but it does matter to what happens after purchase. If one snack needs to be chilled after opening or used quickly once opened, the pack instructions matter. The Food Standards Agency’s food storage guidance is a reminder to follow the product’s own storage instructions where given (Food Standards Agency storage guidance).

So, if the numbers do not settle your question, ask what your question really is.

• Are you comparing energy, fat, sugars, salt or fibre? Use the nutrition table on a matched basis.
• Are you checking what the product is mainly made from? Read the ingredients list.
• Are you checking allergy information? Read the allergen and ingredients information carefully.
• Are you checking whether a claim changes the meaning of the sugars line? Read both the claim and the table.

Those are different tasks. The label can help with all of them, but not if they are muddled together.

Use the result without over-reading it

A label comparison is useful, but it has limits.

It can tell you:

• which snack is higher or lower in listed nutrients on the same basis
• whether a serving size has made a front-of-pack number look smaller
• what the main ingredients are
• whether there are relevant claims or allergen statements to check

It cannot tell you:

• whether a snack is right for every person
• how filling you will find it
• how it fits with everything else you eat across the day or week
• whether one purchase defines your whole diet

That last point matters. The NHS Eatwell Guide frames healthy eating as an overall pattern across a day or week, not a standard that every single snack must meet on its own. For UK adults choosing everyday foods, that is a more realistic and useful context than trying to turn one label comparison into a moral judgement.

At Healthy Snacking, our aim is to make these everyday decisions easier to understand without pretending that labels can answer every question. A fair comparison helps you organise information. It does not need to become a restrictive rule.

If you want the shortest practical method, use this sequence:

1. Check whether both labels are being compared on per 100g or per serving.
2. If the serving sizes differ, go back to per 100g or recalculate to the same amount eaten.
3. Compare the lines you actually care about, usually energy, fat, saturates, sugars, salt and fibre.
4. Then check ingredients, allergens and any claims such as no added sugar.
5. Use the result as one piece of context, not the whole story of your diet.

That is the fairest way to compare two snack labels, especially when you are trying to compare like with like instead of being steered by different serving sizes or front-of-pack marketing.