High fibre vs source of fibre: the GB thresholds
There are two ways to meet a fibre claim. See the per 100g and per 100 kcal rules, with a worked example and portion arithmetic.
On this page
The difference between source of fibre and high fibre is a defined threshold. There are two possible routes to each claim, which is why checking only grams per 100g can miss part of the picture.
What the claim requires
The nutrition claims sheet in the GB register specifies:
| Claim | Fibre per 100g | Alternative: fibre per 100 kcal |
|---|---|---|
| Source of fibre | At least 3g | At least 1.5g |
| High fibre | At least 6g | At least 3g |
A food can meet either column for the relevant claim; it does not have to meet both. This is a Great Britain explainer, covering England, Scotland and Wales. Northern Ireland follows the EU framework, whose published claim conditions list the same thresholds.
Why the energy route matters
Consider a fictional food with 4g fibre and 100 kcal per 100g. It falls below 6g fibre per 100g, but provides 4g fibre per 100 kcal. It reaches the high fibre threshold through the second route.
Now imagine a different food with 4g fibre and 400 kcal per 100g. Its fibre per 100 kcal is:
4 ÷ 400 × 100 = 1g.
It reaches source of fibre using the weight route, but reaches neither high fibre threshold. These are deliberately simple invented labels, not product recommendations.
How much is in your portion?
A fictional food with 6g fibre per 100g supplies 1.8g in a 30g portion: 6 × 30 ÷ 100. The words high fibre do not mean that a small serving contains 6g.
The portion calculator does this scaling without storing your entries. Use the exact value on your packet when one is given, rather than treating the minimum threshold as the product's actual content.
What to compare next
Compare like-for-like portions as well as the per 100g figure. If one packet suggests 20g and another 40g, their per serving numbers alone make an uneven comparison. Our serving-column guide explains how to put them on the same basis.
A fibre claim also leaves other questions open. It does not establish a food's salt, sugar or saturated fat content. It does not tell you whether you like the texture, how it fits a meal or what portion you will actually eat. Read the full panel and ingredients alongside the headline.
For a real ingredient example with an identified dataset, see almonds per 30g. For a different type of claim, compare no added sugar with low sugar.
Sources checked 21 September 2026. Examples are fictional; the calculations explain labels and do not certify a product or prescribe a diet.