How much fiber per day do you need?
Adults need about 14 grams of fiber for every 1,000 calories, according to the Institute of Medicine. Its daily targets are 38 grams for men and 25 grams for women aged 19 to 50, then 30 grams and 21 grams after 50. The UK's NHS recommends 30 grams a day for adults.
Most of us keep an eye on protein, calories, or sugar, and fiber gets left out. Here's a number that surprised me: the NHS says most UK adults eat only about 20 g of fiber a day, against a target of 30 g. The good news is that closing the gap doesn't take fancy foods.
What are the official fiber targets?
In the US, the rule is 14 g of fiber for every 1,000 calories. It comes from the Institute of Medicine (now part of the National Academies). Its 2005 report is also the basis for the US Dietary Guidelines.
The report also sets an "adequate intake." That's a daily amount that should cover most people's needs:
| Age | Men | Women |
|---|---|---|
| 19 to 50 | 38 g | 25 g |
| 51 and older | 30 g | 21 g |
The 14 g per 1,000 calories rule stays the same at every age. If you eat fewer calories, your number by calories goes down with it.
Why do other countries use different numbers?
Each health body sets its own target, but they all land close together. Here's where the numbers you see online come from:
- UK (NHS): 30 g a day for adults.
- World Health Organization: at least 25 g a day of naturally occurring fiber from food for everyone over age 10.
- CDC: 22 to 34 g a day for adults, depending on age and sex.
For most adults, somewhere between 21 g and 38 g a day is the goal.
How do you work out fiber by calories?
Divide your daily calories by 1,000, then multiply by 14. This part is really easy.
| Daily calories | Fiber target |
|---|---|
| 1,600 | 22 g |
| 2,000 | 28 g |
| 2,500 | 35 g |
| 3,000 | 42 g |
Here's an example. Take a 60-year-old woman who weighs 150 lb (68 kg), is 5 ft 4 in (163 cm) tall, and is lightly active. The Mifflin-St Jeor equation puts her at about 1,700 calories a day.
At 14 g per 1,000 calories, that's about 24 g of fiber. Her adequate intake is 21 g. So a goal of 21 to 24 g makes sense for her.
Want your own number? Our fiber calculator does this math for you.
Why does fiber matter?
The NHS says eating plenty of fiber is linked with a lower risk of heart disease, stroke, type 2 diabetes, and bowel cancer. Fiber also helps digestion and can help prevent constipation.
According to the CDC, fiber is a type of carbohydrate. It's found mainly in fruits, vegetables, whole grains, and legumes (beans, peas, and lentils).
There are two main types:
- Soluble fiber dissolves in water and forms a gel in your stomach. This slows digestion. You'll find it in apples, bananas, oats, peas, and beans.
- Insoluble fiber doesn't dissolve. It moves through mostly whole. It's in whole wheat flour, bran, nuts, seeds, and the skins of fruits and vegetables.
Which foods are high in fiber?
Seeds, nuts, beans, lentils, and oats top the list. Here are common foods from USDA data, shown per 100 g (3.5 oz):
| Food | Fiber per 100 g (3.5 oz) |
|---|---|
| Chia seeds, dried | 34.4 g |
| Almonds | 12.5 g |
| Navy beans, cooked | 10.5 g |
| Oats, dry | 10.1 g |
| Black beans, cooked | 8.7 g |
| Lentils, cooked | 7.9 g |
| Chickpeas, cooked | 7.6 g |
| Avocado | 6.7 g |
| Raspberries | 6.5 g |
| Whole-wheat bread | 6.0 g |
| Green peas, cooked | 4.5 g |
| Broccoli, cooked | 3.3 g |
| Sweet potato, baked | 3.3 g |
| Pear | 3.1 g |
| Apple, with skin | 2.4 g |
| Brown rice, cooked | 1.6 g |
You'll usually eat much less than 100 g of chia seeds or almonds at once. So check the portion on the package.
What stands out to me is beans and lentils. They give you fiber and protein together. That's a great combo if you're also chasing a protein goal.
How do you spot high fiber on a label?
The NHS offers a handy rule. A food is high in fiber if it has 6 g or more per 100 g. That's an easy check in the grocery aisle.
What does a 30 g fiber day look like?
Regular meals with a few swaps can get you there. The NHS gives sample meals that show how it adds up:
- Breakfast: 2 slices of wholemeal toast with peanut butter and a medium orange, about 8.3 g
- Lunch: wholemeal spaghetti with lentil and tomato sauce, about 11 g
- Dinner: grilled chicken breast, a skin-on baked potato, carrots, and green beans, about 11.2 g
That's about 30.5 g for the day. No supplements, no strange foods.
Can you get fiber when you eat out?
Yes. Beans, lentils, and edamame are the dishes to look for. A few picks from our restaurant guides:
- Chipotle: the High Protein-High Fiber Bowl has 14 g of fiber and 46 g of protein for 545 calories. See our Chipotle guide.
- Chick-fil-A: the Chicken Tortilla Soup has 17 g of fiber and 24 g of protein for 280 calories.
- itsu (UK): a side of Edamame has 17.4 g of fiber and 10 g of protein for 132 calories.
- Rola Wala (UK): the Red Dal Spice Bowl (Cauli) has 19 g of fiber and 18 g of protein for 338 calories.
Beans, lentils, and edamame show up again and again. That's no accident.
How much fiber do specific groups need?
The core targets don't change much by group. What changes is how you reach them.
On a GLP-1 medicine
If you take a GLP-1 medicine like Ozempic, Wegovy, Zepbound, or Mounjaro, there's no special fiber number. It just gets a little more nuanced.
A 2025 joint advisory from four US nutrition and obesity groups says "adequate fluids and fiber from foods should be encouraged." It also notes that foods high in protein, fat, or fiber can slow stomach emptying further. For some people, that can make constipation worse. It may mean limiting these foods for a while.
So there's no one-size answer here. Work with your doctor or a registered dietitian to find a fiber level that feels good for you. For more on eating well during treatment, see our guide to protein on Ozempic and our page for GLP-1 users.
Women
Women aged 19 to 50 have an adequate intake of 25 g a day, dropping to 21 g after 50. The NHS target of 30 g is a bit higher.
Either way, most women can get there with fruit at breakfast, beans or lentils at lunch, and vegetables at dinner.
Adults 50 and older
Your fiber target goes down slightly after 50 (30 g for men, 21 g for women). But fiber still matters a lot.
The Dietary Guidelines for Americans 2025 to 2030 note that some older adults need fewer calories but still need the same or more of key nutrients. That makes every bite count.
Pairing fiber with protein covers two goals at once. Think beans with chicken, or oats with Greek yogurt. Our guide to protein after 50 has more ideas.
How do you add fiber without discomfort?
Go slowly and drink enough water. The one mistake to avoid is going from 15 g to 35 g overnight. The CDC warns that a sudden jump in fiber can lead to digestive discomfort.
Instead, try this:
- Add one high-fiber food a day. Swap white bread for whole-wheat, or add beans to a salad.
- Spread it out. The CDC suggests increasing fiber gradually across your meals.
- Drink enough water. The CDC says plenty of water helps food move through your system.
- Keep the skins on. The NHS suggests potatoes with skins, and fruit and vegetables where you can.
- Snack smart. The NHS lists fresh fruit, vegetable sticks, rye crackers, oatcakes, and unsalted nuts or seeds.
Give your body a week or two to adjust. Once you find a few go-to foods, it becomes second nature.
When to check with a professional
If you have a digestive condition, kidney disease, diabetes, or take medicines that affect your gut, talk to your doctor or a registered dietitian before making big changes to your fiber intake.
What does this mean for you?
Moving closer to your target matters more than hitting it exactly. Based on what I've seen in the research, that's the biggest win. If you eat 15 g now, getting to 22 g is real progress.
Start with foods you already like. Beans in your chili. Oats at breakfast. An apple with the skin on. Small swaps add up fast.
The bottom line
For most adults, the target is 14 g of fiber per 1,000 calories. That usually lands between 21 g and 38 g a day, depending on your age and sex. The NHS rounds it to 30 g for UK adults.
You don't need supplements or special products to get there. Beans, lentils, whole grains, fruit, vegetables, nuts, and seeds will do the job. Get your personal target with our fiber calculator, then add one fiber-rich food at a time. You've got this.