Fiber intake calculator
Enter how many calories you eat a day. You get the fibre figure that goes with it, plus the US adequate intake for your age and sex and the European reference value.
Updated
A reference figure, not a personal target and not medical advice. If you eat little fibre now, raise it gradually; bowel conditions or a medication that slows digestion are worth a word with your clinician first.
The formula this calculator uses
From calories (large number)
fibre (g/day) = calories ÷ 1000 × 14, shown to one decimal [1].
By age and sex (NASEM line)
age 19–50: men 38 g, women 25 g · age 51 and over: men 30 g, women 21 g [1]. Blank if age is empty or under 19.
EFSA and per meal
EFSA line: 25 g for adults [2] · per 3 meals = calorie-based figure ÷ 3.
Worked examples
Each row was entered into this calculator and the result copied as shown.
| Entry | From calories | NASEM for your age | EFSA | Per 3 meals |
|---|---|---|---|---|
| 1,200 kcal · age left blank | 16.8 g | – | 25 g | 5.6 g |
| 1,800 kcal · female · 45 | 25.2 g | 25 g | 25 g | 8.4 g |
| 2,400 kcal · male · 60 | 33.6 g | 30 g | 25 g | 11.2 g |
What this calculator does not do
- It does not tell you how much fibre to eat or how fast to increase it.
- It does not diagnose or treat constipation, diarrhoea or any bowel condition.
- It does not estimate your calories; enter them yourself or use the TDEE calculator.
- It does not give values for children; the age line starts at 19.
About this estimate and your privacy
The calorie-based figure follows the NASEM rule of 14 g per 1,000 kcal [1]. If you eat less than you used to, the figure drops with your intake; the age-based line does not.
Everything is worked out by a script inside this page. The script makes no network requests, the page’s security policy (Content-Security-Policy with default-src none and no connect-src) would block them anyway, and nothing you type is stored, not even in your browser’s storage. Reload the page and the fields are empty again.
Next to each source below is what it supports on this page.
Ozempic® is a trademark of Novo Nordisk A/S. Mounjaro® is a trademark of Eli Lilly and Company. PepLabo is not affiliated with or endorsed by them.
Questions
Why does the calorie figure differ from the age table?
The age and sex values come from the same 14 g per 1,000 kcal rule applied to typical energy intakes [1]. If you eat less or more than that, the calorie-based figure follows your own intake.
What if I eat very little on a GLP-1 medication?
Then the calorie-based figure drops with your intake. Whether to aim for the age-based value instead is a good question for your clinician or dietitian, especially since constipation is among the most common adverse reactions in these labels [3][4].
Is constipation common on GLP-1 medications?
Yes. It is listed among the most common adverse reactions in the Ozempic® and Mounjaro® labels [3][4], and post-marketing reports in the Ozempic® label include severe constipation with fecal impaction [3].
Where does the EFSA value of 25 g come from?
EFSA’s 2010 opinion on carbohydrates and dietary fibre considers 25 g a day adequate for adults [2]. It is a single adult value, which is why the line does not change with age or sex.
Why is there a per-meal line?
It simply divides the calorie-based figure by three, to show what the total looks like spread over a day. It is not a meal plan.
Why is age optional?
Age only changes the NASEM line, because NASEM gives separate values for 19–50 and 51 and over [1]. The calorie-based figure does not depend on age.
Does the calculator work for children?
No. NASEM sets separate values for children [1], and the age line here only covers adults from 19.
Does PepLabo track fibre?
Yes. When you log a meal in PepLabo, fibre is recorded next to protein, carbs and fat, so you can see the day’s total.
Sources
Sources checked on
- National Academies (NASEM). Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids (2005) Supports: adequate intake of 14 g fibre per 1,000 kcal; values by age and sex.
- EFSA Panel on Dietetic Products, Nutrition and Allergies. Scientific Opinion on Dietary Reference Values for carbohydrates and dietary fibre. EFSA Journal 2010;8(3):1462 Supports: 25 g a day considered adequate for adults.
- Ozempic® (semaglutide) injection: US prescribing information, Novo Nordisk (DailyMed) Supports: constipation among the most common adverse reactions; post-marketing severe constipation with fecal impaction.
- Mounjaro® (tirzepatide) injection: US prescribing information, Eli Lilly and Company (DailyMed) Supports: constipation among the most common adverse reactions.
Set up your lab tonight.
It takes a few minutes. Pep will be waiting.