Fibre Intake Calculator (14 g per 1,000 kcal)

Understanding the fibre intake calculator — concept and principle

Dietary fibre is the part of plant food that the small intestine cannot digest. It supports regular bowel movements, feeds gut bacteria and is linked to lower risk of heart disease and type 2 diabetes. This calculator sets a fibre target that scales with how much you eat and shows how far your current intake is from it.

The target scales with how much you eat: 2,000 kcal → 28 g, so 15 g leaves 13 g to add.

How it is calculated

Recommended fibre (g) = daily calories ÷ 1,000 × 14
Gap (g) = recommended fibre − your current fibre

Calories are kilocalories per day; fibre is in grams per day. A positive gap is how much you need to add; a negative gap means you are already above the target.

The principle

The figure of 14 g per 1,000 kcal comes from the US Institute of Medicine's Dietary Reference Intakes, which set an Adequate Intake for fibre based on intakes associated with the lowest risk of coronary heart disease in large cohort studies. Expressing the target per 1,000 kcal makes it fair for small and large eaters: someone eating more food has more room for fibre-rich foods. Applied to typical energy needs, it gives about 25 g a day for women and 38 g for men aged 19–50, and about 21 g and 30 g after age 50. The US Dietary Guidelines use the same 14 g per 1,000 kcal benchmark.

Worked example

Default inputs: 2,000 kcal per day, current fibre 15 g.
Recommended = 2,000 ÷ 1,000 × 14 = 28 g.
Gap = 28 − 15 = 13 g.

The calculator shows 28 g recommended and a gap of 13 g.

Each point is the calculator re-run with only “Daily calories” changed; the gold point is the default example. Change the inputs above and this chart follows your numbers.

Daily calories	Recommended fibre (g)
500	7
1,000	14
1,500	21
2,000	28
2,500	35
3,000	42
4,000	56

How to read the result

Most adults in Western countries eat well below the target, often around 15 g a day, so a gap of 10–15 g is common. You can close 13 g with, for example, a serving of cooked lentils or beans, a piece of fruit with the skin and a switch from white to wholegrain bread. Raise intake gradually over a few weeks and drink enough fluid; a sudden jump can cause gas and bloating. Variety matters as much as the total.

Common mistakes

Entering a weight-loss calorie target that is far below what you actually eat, which understates the target.
Counting the "total carbohydrate" line instead of the "dietary fibre" line on labels.
Relying only on supplements; whole foods bring vitamins, minerals and other plant compounds as well.

Keep in mind: This is a general guideline, not a diagnosis. People with inflammatory bowel disease, a recent bowel operation or a narrowed intestine may be told to limit fibre, so follow your doctor's advice.

Frequently asked questions

Is soluble or insoluble fibre better?

You need both. Soluble fibre forms a gel and can lower cholesterol and blunt blood-sugar rises; insoluble fibre speeds transit and adds stool bulk.

Can I eat too much fibre?

There is no official upper limit, but very high intakes without enough fluid can cause bloating or constipation and may reduce absorption of some minerals.

Sources: Institute of Medicine. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. National Academies Press, 2005. · U.S. Department of Agriculture and U.S. Department of Health and Human Services. Dietary Guidelines for Americans, 2020–2025.

Checked 8 Nov 2026. Published formulas cited on the page. For information only — not medical advice.

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