What this calculator works out
This calculator compares your daily fibre intake against a target, showing the shortfall or surplus per day and the cumulative figure across the number of days you choose.
The cumulative view is the useful part. A ten gram daily gap sounds minor and looks different expressed as seventy grams across a week.
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Before you compare
- The UK recommendation for adults is 30 g of fibre a day. Average intakes are closer to 20 g.
- Get intake figures from food labels, which give fibre per 100 g and per portion, or from a food tracking app.
- Children need less: broadly 15 g for ages 2 to 5, 20 g for 5 to 11 and 25 g for 11 to 16.
- Use a typical day rather than an unusually good or bad one.
Soluble fibre — oats, beans, apples, barley — forms a gel in the gut and helps lower cholesterol and slow glucose absorption. Insoluble fibre — wholemeal bread, bran, nuts, many vegetables — adds bulk and speeds transit. Most fibre-rich foods contain both, so there is rarely any need to track them separately.
How this calculator works
A comparison expressed three ways:
Share of target = intake ÷ target × 100
Per day = intake − target
Over the period = (intake − target) × daysThe target is an editable field so you can use the figure appropriate to your age, or one a dietitian has given you. The calculator makes no judgement about intakes above the target — very high fibre intakes are uncommon and rarely problematic in healthy adults, though they can aggravate some gut conditions.
Worked example: 20 g against a 30 g target
Using the default figures — 20 g a day against a 30 g target, over 7 days:
- Share of target: 67%
- Per day: 10 g below
- Over 7 days: 70 g below
Closing a ten gram daily gap is more achievable than it sounds. Switching to wholemeal bread adds around 3 g across two slices, a portion of beans adds 5 g, and a pear with the skin on adds 3 g. Three small substitutions cover it — which is a considerably more useful conclusion than the 67% figure on its own.
Common mistakes
- Increasing intake suddenly. A sharp rise commonly causes bloating and wind; increase over a few weeks.
- Not increasing fluid alongside. Fibre needs water to work properly and can worsen constipation without it.
- Assuming brown always means wholegrain. Check the label; colour is not a reliable guide.
- Relying on supplements. Fibre-rich foods bring vitamins, minerals and other compounds that isolated fibre does not.
- Using adult targets for children. Recommendations are lower and rise with age.
Frequently asked questions
Why is fibre important?
Higher fibre intakes are associated with lower risk of heart disease, stroke, type 2 diabetes and bowel cancer, and fibre supports regular bowel function and the gut microbiome. It is one of the few dietary recommendations where the UK population average sits clearly below the target, which is why it receives so much attention in public health guidance.
What are the easiest ways to increase it?
Swap white bread, rice and pasta for wholemeal or wholegrain versions; leave skins on potatoes and fruit; add beans or lentils to dishes you already make; choose a high-fibre breakfast cereal; and keep nuts or fruit as snacks. These changes require no new recipes and typically add 10 to 15 g a day between them.
Does fruit juice count?
Very little. Juicing removes most of the fibre, which is why a glass of juice and a whole orange are nutritionally quite different despite similar sugar content. Whole fruit is the better choice for fibre, and NHS guidance counts juice as only one of your five a day regardless of quantity.
I have IBS. Should I increase fibre?
Not necessarily, and possibly not in the way general advice suggests. Some people with IBS improve on more soluble fibre and worsen on more insoluble fibre, and specialist dietary approaches are usually managed with a dietitian. Take this to your GP or a registered dietitian rather than applying a general target.
Is what I enter stored?
No. Intake figures are processed in your browser and never transmitted or retained. If thinking about food or eating is causing you distress, tracking intake against a target may make that harder rather than easier. Beat, the UK eating disorder charity, runs a free helpline and online support, and a GP can refer you to specialist services.
Related tools
References
- NHS — fibre recommendations and practical ways to increase intake
- GOV.UK — Scientific Advisory Committee on Nutrition report on carbohydrates and health
Sources are checked at publication and can change — how I choose and check references.