Fibre Intake Calculator
How much dietary fibre you need a day from your energy intake — the 14 grams per 1,000 kcal rule — and how far your current intake is from it, in real foods.
Dietary guidelines around the world land on 25–38 g of fibre a day for adults, and the most portable rule is 14 g for every 1,000 kcal eaten: 2,000 kcal calls for 28 g.
How the fibre intake calculator works
Dietary guidelines around the world land on 25–38 g of fibre a day for adults, and the most portable rule is 14 g for every 1,000 kcal eaten: 2,000 kcal calls for 28 g. Most people get about half that. Enter what you currently eat and the calculator shows the gap and what would fill it — an apple is about 4 g, a cup of cooked lentils 15 g, a slice of wholegrain bread 2 g.
Formula: fibre (g/day) = calories ÷ 1,000 × 14
Worked examples
| Inputs | Fibre target | Note |
|---|---|---|
| 2,000 kcal, currently 18 g | 28 g/day | 28 g — 10 g short |
| 8,700 kJ | 29 g/day | 29 g |
| 2,800 kcal athlete | 39 g/day | 39 g |
FAQFrequently asked questions
Where does 14 g per 1,000 kcal come from?
From the intake associated with the lowest risk of heart disease in large cohort studies; it is the basis of the US Adequate Intake and close to the figures other countries publish (25 g for women and 30 g for men in Australia, 30 g for adults in the UK).
What counts as fibre?
Plant carbohydrate the gut does not digest: soluble fibre in oats, beans and fruit, insoluble in wholegrains and vegetable skins, and resistant starch in cooled potatoes and rice. Labels list total fibre.
How fast should I increase it?
Gradually, over a couple of weeks, with more water — a sudden jump causes bloating and wind. Spread it across meals rather than loading one.
Can I have too much?
Above about 50–60 g a day some people get discomfort and slightly reduced mineral absorption, but for most the problem runs the other way. If you have a bowel condition, ask your doctor first.
Where these figures come from
- US FDA — Safe Minimum Internal Temperatures — the internal temperatures the roasting calculator targets
- NIST SP 811 — Guide for the Use of the International System of Units — the exact weight and volume conversions used throughout
- US Food and Drug Administration — food safety and labelling standards
Last checked: September 2026. Baking ratios follow standard baker's percentage practice; roasting guidance follows published safe internal temperatures.