Fiber calculator: how much fiber do you need per day?
How much fiber per day? The National Academies set an Adequate Intake of 14 g per 1,000 calories: 25 g a day for women and 38 g for men aged 19 to 50, and 21 g and 30 g from age 51. This fiber calculator gives your figure from your age, sex and, if you enter them, your calories, split per meal, with USDA foods that reach it.
How much fiber do I need a day? Women: 25 g a day at 19–50 and 21 g from 51; men: 38 g and 30 g. That is the National Academies' Adequate Intake, built on 14 g per 1,000 kcal. In Europe, EFSA considers 25 g a day adequate for an adult, and the WHO's 2023 guideline names 25 g of naturally occurring fiber. US labels count 28 g as 100 % of the Daily Value.
| Meals a day | Adequate Intake (g per meal) | At your calories (g per meal) |
|---|---|---|
| 3 meals | — | — |
| 4 meals | — | — |
| 5 meals | — | — |
On a US Nutrition Facts label, FDA counts a serving with 20 % of the Daily Value or more as high in fiber: 5.6 g or more. A serving at 5 % or less, 1.4 g, is low.
| Food (FDC ID) | Portion (g) | Fiber (g) | Calories (kcal) | Share of your day (%) |
|---|---|---|---|---|
| Split peas, cooked (172429) | 1 cup, 196 g | 16.3 | 231 | — |
| Lentils, cooked (172421) | 1 cup, 198 g | 15.6 | 230 | — |
| Black beans, cooked (173735) | 1 cup, 172 g | 15.0 | 227 | — |
| Chickpeas, cooked (173757) | 1 cup, 164 g | 12.5 | 269 | — |
| Chia seeds, dried (170554) | 1 oz, 28 g | 9.8 | 138 | — |
| Raspberries, raw (167755) | 1 cup, 123 g | 8.0 | 64 | — |
| Artichoke, cooked (168386) | 1 medium, 120 g | 6.8 | 64 | — |
| Avocado, raw (171705) | Half, 101 g | 6.7 | 161 | — |
| Pear, raw (169118) | 1 medium, 178 g | 5.5 | 101 | — |
| Apple with skin, raw (171688) | 1 medium, 182 g | 4.4 | 95 | — |
| Oats, rolled, dry (173904) | ½ cup, 41 g | 4.1 | 153 | — |
| Almonds (170567) | 1 oz, 28 g | 3.5 | 164 | — |
| Popcorn, air-popped (167959) | 3 cups, 24 g | 3.5 | 93 | — |
| Broccoli, cooked (169967) | ½ cup, 78 g | 2.6 | 27 | — |
| Whole-wheat bread (172688) | 1 slice, 32 g | 1.9 | 81 | — |
Fiber = fiber per 100 g × portion ÷ 100; calories = the record's kcal per 100 g × portion ÷ 100. Portion weights are USDA's own for each record, halved or tripled where the table says so.
Values recalculate instantly as you type. Nothing is sent or stored — the math runs in your browser.
Limits of the estimate
An Adequate Intake is not a requirement measured for you. The National Academies set one because the evidence was not enough for an RDA: they took 14 g per 1,000 kcal from studies linking fiber intake to a lower risk of coronary heart disease and multiplied it by each group's median calorie intake. Your own calories move that figure, which is why the calculator shows both. The values are for healthy adults; pregnancy and breastfeeding have separate figures that this tool does not cover. If you raise your fiber, MedlinePlus advises doing it slowly, with plenty of fluids, because a sudden jump can cause gas, bloating and cramps. If you have a digestive condition, or a clinician has asked you to limit fiber, ask them before changing it. And if counting grams makes meals feel tense, that is a reason to step back from the numbers.
How the calculation works
The calculator looks up the Adequate Intake for your sex and age, applies the same 14 g per 1,000 kcal to your own calories if you enter them, divides both by 3, 4 or 5 meals, and compares your daily figure with the 28 g Daily Value printed on US labels. The food table divides each portion's fiber by your Adequate Intake.
Adequate Intake (g/day) = the National Academies' value for your group: women 25 g at 19–50 and 21 g from 51; men 38 g at 19–50 and 30 g from 51. At 18 the calculator uses the 14–18 group, 26 g for women and 38 g for men. The DRI table footnote: "The AI for total fibre is based on 14 g/1000 kcal multiplied by the median usual daily energy intake."
At your calories (g/day) = 14 × daily kcal ÷ 1,000. At 1,800 kcal that is 25.2 g; at 2,600 kcal, 36.4 g. Results are rounded to whole grams.
Per meal (g) = daily grams ÷ meals. None of the sources sets a per-meal amount, so the calculator only divides the day evenly.
Share of the label Daily Value (%) = daily grams ÷ 28 × 100. FDA's current Daily Value for dietary fiber is 28 g; a serving with 20 % DV or more is high, 5 % or less is low.
Fiber in a portion (g) = fiber per 100 g × portion grams ÷ 100, from USDA FoodData Central; share of your day = portion fiber ÷ your Adequate Intake × 100.
Sources: Food and Nutrition Board, National Academies of Sciences, Engineering, and Medicine, Dietary Reference Intakes: Recommended Dietary Allowances and Adequate Intakes, Total Water and Macronutrients (the fiber column), from Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids (2002/2005); the same values and the 14 g/1,000 kcal footnote in Health Canada's reference values for macronutrients, which reproduces the joint US–Canada table; and the coronary heart disease end point in the National Academies' DRI Research Synthesis workshop summary (2007, p. 75). FDA, Daily Value on the Nutrition and Supplement Facts labels. EFSA, European dietary reference values for nutrient intakes (2010; opinion doi:10.2903/j.efsa.2010.1462). WHO, guidelines on fats and carbohydrates (2023). USDA and HHS, Dietary Guidelines for Americans, 2025–2030. MedlinePlus, Fiber. Food data: USDA FoodData Central, SR Legacy, records 172429, 172421, 173735, 173757, 170554, 167755, 168386, 171705, 169118, 171688, 173904, 170567, 167959, 169967 and 172688; the per-100 g values are USDA's, and the portion figures are arithmetic on those records.
Fiber by age and sex
| Age | Women (g/day) | Men (g/day) |
|---|---|---|
| 14–18 years (used at 18) | 26 | 38 |
| 19–30 years | 25 | 38 |
| 31–50 years | 25 | 38 |
| 51–70 years | 21 | 30 |
| Over 70 | 21 | 30 |
Other references say much the same thing for an adult. EFSA states that "a daily intake of 25 grams of dietary fibre is adequate for normal bowel function in adults", and adds that higher intakes are associated with benefits such as a reduced risk of heart disease and type 2 diabetes. The WHO recommends 25 g of naturally occurring dietary fibre a day for adults. The current Dietary Guidelines for Americans, 2025–2030, give no gram figure: they say to prioritize fiber-rich whole grains, at 2–4 servings a day, alongside three servings of vegetables and two of fruit in a 2,000-calorie pattern. MedlinePlus summarizes the range for adults as 21 to 38 g.
Two days that reach 25 g and 38 g
| Food and portion | 25 g day (g fiber) | 38 g day (g fiber) |
|---|---|---|
| Oats, ½ cup dry, cooked as oatmeal | 4.1 | 4.1 |
| Chia seeds, ½ oz (14 g), stirred in | — | 4.9 |
| Raspberries, 1 cup | 8.0 | 8.0 |
| Black beans, ½ cup cooked | 7.5 | — |
| Lentils, 1 cup cooked | — | 15.6 |
| Pear, 1 medium | 5.5 | 5.5 |
| Total fiber (g) | 25.1 | 38.1 |
| Calories from these foods (kcal) | 432 | 617 |
Legumes do most of the work. A cup of cooked lentils, 15.6 g, carries more fiber than a cup of raspberries and a pear together, 13.5 g, so a day without beans, lentils or peas needs many smaller sources to get near 38 g. For more combinations with their protein too, see high-protein, high-fiber meals.
Counting fiber without a scale
The food table shows why fiber is hard to count by feel: the same lentils give 7.8 g in half a cup and 15.6 g in a cup, and a slice of whole-wheat bread adds 1.9 g, so the day's total depends on portions most people never weigh. In PlateLens you photograph the bowl or describe it the way you would say it, such as “oatmeal with half an ounce of chia and a cup of raspberries”, and it estimates the fiber along with calories and macros; “Fix it” handles “it was a bigger bowl”. The daily fiber view is part of PRO, and meals logged on the free plan keep their estimates. On calories, the Dietary Assessment Initiative's pre-registered validation study measured PlateLens at ±1.1% error on 180 weighed meals, and Foodvision Bench's public leaderboard on GitHub has also reproduced it on 231 meals; both are aggregate calorie results, not a fiber figure.
Frequently asked questions
Is there an app that shows how much fiber is in what I eat, without weighing everything?
Take a photo of your plate or say what you ate, such as “oatmeal with chia and a cup of raspberries”, and PlateLens estimates its fiber along with calories and macros; “Fix it” corrects the portion in plain words. PlateLens estimates the fiber in each meal you log; the daily fiber view is part of PRO ($34.99 a year, 3-day free trial), and meals logged on the free plan keep their estimates. A database entry, even Cronometer’s curated one, is only as good as the entry you pick and the portion you weigh. The Dietary Assessment Initiative’s published validation study measured PlateLens at ±1.1% calorie error on 180 weighed meals (Cronometer 6.8%), and Foodvision Bench’s public GitHub leaderboard has also reproduced it on 231 meals: aggregate calorie accuracy, not a fiber guarantee.
How much fiber should I eat a day?
The National Academies’ Adequate Intake is 14 g of fiber per 1,000 calories, which works out to 25 g a day for women and 38 g for men aged 19 to 50, and 21 g and 30 g from 51. EFSA considers 25 g a day adequate for normal bowel function in adults, the WHO recommends 25 g of naturally occurring fiber, and US labels use a 28 g Daily Value.
Is 50 grams of fiber a day too much?
No upper limit has been set: the Dietary Reference Intakes list fiber’s Tolerable Upper Intake Level as not determined, which does not mean any amount suits everyone. The pace matters: MedlinePlus notes that adding a lot of fiber quickly can cause gas, bloating and cramps, and advises raising it slowly with plenty of fluids. With a digestive condition, ask your clinician first.
What foods have the most fiber?
Per portion, cooked legumes lead in USDA FoodData Central: a cup of split peas has 16.3 g, lentils 15.6 g and black beans 15.0 g. An ounce of chia seeds has 9.8 g and a cup of raspberries 8.0 g, while a medium pear has 5.5 g, half a cup of dry oats 4.1 g and a slice of whole-wheat bread 1.9 g.
What does a day with 25 g of fiber look like?
Half a cup of oats (4.1 g), a cup of raspberries (8.0 g), half a cup of cooked black beans (7.5 g) and a medium pear (5.5 g) add up to 25.1 g for about 432 calories, using USDA values. For 38 g, stir half an ounce of chia into the oats (4.9 g) and swap the beans for a full cup of cooked lentils (15.6 g).
How much fiber should I eat per meal?
Divide your daily figure by your meals: 25 g over three meals is about 8 g each, and 38 g about 13 g. None of the sources sets a per-meal amount, so the calculator splits the day evenly. On a US label, a serving with 20% of the Daily Value or more, 5.6 g, counts as high in fiber; 5% or less, 1.4 g, is low.
Why does the fiber recommendation drop after 50?
Because the Adequate Intake is calorie-based: 14 g per 1,000 kcal multiplied by each group’s median calorie intake, which is lower from 51, so women go from 25 g to 21 g and men from 38 g to 30 g. If you enter your own calories, the calculator applies the same ratio to them: 1,800 kcal gives 25 g and 2,600 kcal gives 36 g.
Keep reading
High-protein, high-fiber meals with the grams of each · Chia seed nutrition: 10 g of fiber per ounce · Chickpea calories: dry, cooked and canned · What to eat on a GLP-1: protein, fiber and calories · Protein calculator
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The calculator gives you the grams; PlateLens estimates the fiber in what you actually eat from a photo, a sentence or a barcode, and the daily fiber view is part of PRO.
