Dietary fibre is the part of plant foods that your body cannot fully digest. That sounds like a shortcoming, but it is why fibre is so useful: it adds bulk that keeps the bowel regular, feeds beneficial gut bacteria, slows the absorption of sugar, and binds cholesterol-containing bile acids so they leave the body. People who eat more fibre have lower rates of heart disease, type 2 diabetes and bowel cancer. Yet most adults in the United States eat only about half of the recommended amount. This calculator gives you your target from the Institute of Medicine’s Adequate Intakes, plus the figure implied by the 14 grams per 1,000 calories rule.
How to use the fiber intake calculator
- Choose the group that matches you: child, teen, adult man or woman, pregnant or breastfeeding.
- Optionally enter your daily calories to see the calorie-based target.
- Read the Adequate Intake in grams (and ounces).
- Compare with your diet by adding up the dietary fibre line on food labels.
Fibre formula
or 14 g × (daily calories ÷ 1,000)
| Group | Adequate Intake (g per day) |
|---|---|
| Children 1–3 | 19 |
| Children 4–8 | 25 |
| Boys 9–13 | 31 |
| Girls 9–13 | 26 |
| Boys 14–18 | 38 |
| Girls 14–18 | 26 |
| Men 19–50 | 38 |
| Women 19–50 | 25 |
| Men 51 and over | 30 |
| Women 51 and over | 21 |
| Pregnant women | 28 |
| Breastfeeding women | 29 |
The Adequate Intakes are from the Institute of Medicine, Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids (2005). They were set at 14 g per 1,000 kcal, the intake associated with the greatest protection against coronary heart disease in prospective studies, multiplied by the median energy intake for each group.
Worked example
A woman aged 35 who eats 2,000 kcal a day.
- Adequate Intake (women 19–50): 25 g a day, or 0.88 oz.
- Calorie-based target: 14 × 2,000 ÷ 1,000 = 28 g.
- A man aged 35 eating 2,800 kcal: Adequate Intake 38 g; calorie-based 14 × 2.8 = 39.2 g.
Fibre by calorie level
| Calories per day | Fibre at 14 g per 1,000 kcal |
|---|---|
| 1,200 | 16.8 g |
| 1,500 | 21.0 g |
| 1,800 | 25.2 g |
| 2,000 | 28.0 g |
| 2,200 | 30.8 g |
| 2,500 | 35.0 g |
| 3,000 | 42.0 g |
Getting enough fibre
- Swap refined for whole grains. Whole-grain bread, brown rice and oats add several grams a day.
- Eat legumes often. Beans, lentils and chickpeas are among the richest sources.
- Keep skins on fruit and vegetables and eat nuts and seeds.
- Raise intake gradually and drink water to limit gas and bloating.
- Read labels. A food with 5 g or more of fibre per serving is considered a high-fibre source (FDA).
Fibre and low-carb diets
People who restrict carbohydrate often fall short of fibre. If you count net carbs, fibre is subtracted from the total, so a high-fibre low-carb diet is possible; see the Net Carb Calculator, Keto Calculator and Carb Calculator. For wider nutrition planning use the Macro Calculator, Calorie Calculator and Water Intake Calculator, since extra fibre works best with enough fluid.
This page is for information only and is not medical or dietary advice. Speak to a doctor or registered dietitian before changing your diet, especially if you have diabetes, kidney disease, are pregnant or take medicines.
Sources
- Institute of Medicine. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. National Academies Press, 2005.
- US Department of Agriculture and Department of Health and Human Services. Dietary Guidelines for Americans, 2020–2025.
- US Food and Drug Administration. Nutrient content claims: “high fibre” (5 g or more per serving).
Frequently asked questions
How much fibre should I eat per day?
The US Institute of Medicine’s Adequate Intakes are 25 g a day for women and 38 g for men aged 19 to 50, falling to 21 g and 30 g after 50 because people tend to eat less. The figures are based on 14 g of fibre per 1,000 calories, the amount linked with lower heart disease risk.
Why is fibre important?
Fibre supports bowel regularity, helps lower LDL cholesterol (especially soluble fibre from oats, beans and fruit), slows glucose absorption and is associated with lower risk of heart disease, type 2 diabetes and some cancers. Most people in the US and UK eat well below the recommendations.
How can I increase fibre safely?
Add it gradually over a few weeks and drink more fluid to avoid bloating and gas. Beans, lentils, whole grains, vegetables, fruit with the skin, nuts and seeds are the main sources. Check labels for the dietary fibre line.
Can you eat too much fibre?
Very high intakes can cause bloating, gas and reduce absorption of some minerals, but there is no established upper limit for healthy people. If you have inflammatory bowel disease or other digestive conditions, follow your clinician’s advice.
Is a fibre supplement as good as food?
Supplements can help but do not provide the vitamins, minerals and phytochemicals found in whole foods, and effects on cholesterol and fullness vary by fibre type. Food first is the usual advice.