Introduction
Fiber is a key part of a healthy diet. It helps your body digest food, keeps your gut healthy, and can lower your risk of heart disease and diabetes.2 Most people don't get enough fiber each day. Adults need between 25 and 38 grams of fiber daily, but the exact amount depends on your age, sex, and how many calories you eat.1 This Fiber Calculator makes it easy to find out how much fiber you should be eating each day. Just enter a few simple details about yourself, and the calculator will give you a personalized daily fiber goal. Use this tool to make sure you're getting the right amount of fiber to support good health.
How to Use Our Fiber Calculator
Enter a few details about yourself below, and our fiber calculator will tell you how many grams of fiber you should eat each day based on your age and sex.
Age: Enter your current age in years. Fiber needs change as you grow, so this helps us give you the right amount.
Sex: Select your biological sex. Males and females have different daily fiber needs, so this matters for an accurate result.
Pregnant or Breastfeeding (if applicable): If you are pregnant or breastfeeding, select the option that applies to you. Your body needs more fiber during these times.
What Is Dietary Fiber and How Much Do You Need?
Dietary fiber is the part of plant foods that your body cannot fully digest or absorb. Unlike fats, proteins, and carbohydrates, which your body breaks down and uses for energy, fiber passes through your stomach, small intestine, and colon mostly intact. Despite not being digested, fiber plays a critical role in keeping your body healthy. It helps with digestion, keeps your bowel movements regular, lowers cholesterol levels, controls blood sugar, and helps you feel full longer after eating.
Types of Fiber
There are two main types of dietary fiber, and both are important:
- Soluble fiber dissolves in water and forms a gel-like substance in your gut. It helps lower blood cholesterol and blood sugar levels. Good sources include oats, beans, apples, citrus fruits, barley, and psyllium husk.
- Insoluble fiber does not dissolve in water. It adds bulk to your stool and helps food move through your digestive system more quickly. Good sources include whole wheat flour, wheat bran, nuts, vegetables like cauliflower and green beans, and potatoes with their skin.
Most plant foods contain both types of fiber in varying amounts, so eating a wide variety of fruits, vegetables, whole grains, legumes, nuts, and seeds is the best way to get enough of each kind.
How Much Fiber Do You Need Each Day?
The amount of fiber you need depends on your age, sex, and how many calories you eat. The Institute of Medicine (IOM) set general guidelines called Adequate Intake (AI) values, listed here from the National Academies' DRI tables.1
- Men ages 19–50: 38 grams per day1
- Men ages 51 and older: 30 grams per day1
- Women ages 19–50: 25 grams per day1
- Women ages 51 and older: 21 grams per day1
- Children ages 1–8: 19–25 grams per day1
- Teens ages 9–18: 26–38 grams per day, depending on sex1
- Pregnancy: 28 grams per day; breastfeeding: 29 grams per day1
The AI values themselves rest on a calorie-based rule of 14 grams of fiber for every 1,000 calories eaten.2 This calculator applies both the fixed values and the calorie rule and suggests you aim for whichever number is higher.
Most People Don't Eat Enough Fiber
The average American eats only about 16 grams of fiber per day, well short of the recommendation.3 Only about 5% of the population meets the recommended intake, a shortfall sometimes called the "fiber gap."2 Low fiber intake is linked to higher rates of heart disease, type 2 diabetes, obesity, and certain types of cancer.2
Easy Ways to Increase Your Fiber Intake
Boosting your fiber does not have to be complicated. Here are some simple strategies:
- Choose whole grains over refined grains. Swap white bread for whole wheat bread and white rice for brown rice or quinoa.
- Eat more legumes. Beans, lentils, and chickpeas are among the highest-fiber foods available.
- Snack on fruits, vegetables, and nuts instead of processed snacks.
- Leave the skin on fruits and vegetables like apples, pears, and potatoes when possible, since much of the fiber lives in the skin.
- Add seeds like chia or flaxseed to oatmeal, yogurt, or smoothies for a quick fiber boost.
Important Tips When Adding Fiber
If you currently eat very little fiber, increase your intake gradually over a few weeks rather than all at once. A sudden large increase can cause gas, bloating, and cramping. Also, be sure to drink plenty of water as you add more fiber to your diet. Fiber works best when it absorbs water, which helps your stool stay soft and move easily through your digestive system.
Fiber is just one piece of the nutrition puzzle. Getting the right balance of protein alongside adequate fiber supports muscle maintenance, satiety, and overall health.
This fiber calculator gives you a personalized daily fiber goal based on your age, sex, height, and weight. It estimates your calorie needs using the Mifflin-St Jeor equation, published in 1990,4 and then applies the 14 grams per 1,000 calories rule behind the Adequate Intake.2 The daily fiber tracker lets you log the foods you eat and see how close you are to meeting your goal throughout the day.