Fiber Intake Calculator

About the Fiber Intake Calculator

This Fiber Intake Calculator estimates your daily fiber target (g/day) by first estimating calories with the Mifflin–St Jeor equation (from age, sex, height, weight) and an activity factor, then applying the 14 g per 1000 kcal rule. For context it also shows the Adequate Intake (AI) by age and sex.

Practical ways to hit your target: beans and lentils, whole grains, oats, fruit and vegetables, chia or flax seeds, and nuts. Increase fiber gradually and drink water to minimize GI discomfort.

Educational tool — not medical or dietary advice.

FAQ

• How is my fiber target calculated?
  We estimate calories with the Mifflin–St Jeor equation (age, sex, height, weight) plus your activity level (PAL) to get TDEE, then apply 14 g per 1000 kcal. We also show AI (Adequate Intake) by age/sex for comparison.
• Which should I follow: 14 g/1000 kcal or AI?
  Use the kcal-based target for a personalized goal (it scales with how much you eat). Use AI as a benchmark (e.g., ~25 g women, ~38 g men; lower after 50). If they’re close, you’re in the right range.
• What does “AI” mean?
  AI = Adequate Intake — a population guideline set by nutrition authorities when an exact RDA isn’t defined. It’s a practical daily target by age and sex.
• Do I need to enter today’s intake?
  No. This calculator gives a daily target. If you track food later (app/diary), compare its total grams of fiber to this target.
• Does body size or activity change my target?
  Yes for the kcal-based method (higher TDEE ⇒ higher fiber target). AI values don’t depend on calories; they depend on age/sex.
• Soluble vs insoluble fiber — do I need to split them?
  Not for this target. Aim for total dietary fiber; most diets naturally include both types when you eat varied plant foods.
• Can I increase fiber quickly?
  Increase gradually and hydrate. A sudden jump can cause gas/bloating. Add beans/lentils, oats, whole grains, fruit/veg, chia/flax.
• Is there such a thing as too much fiber?
  Very high intakes may cause GI discomfort or affect absorption for some people. Build up slowly and adjust if symptoms persist.
• Low-carb or weight-loss diets: any change?
  The kcal-based target will drop if your calories drop, but prioritize high-fiber, lower-energy foods (vegetables, berries, legumes in portions that fit your plan).
• What foods are naturally high in fiber?
  Beans, lentils, chickpeas, oats, barley, whole-grain breads/pasta, berries, pears, apples, broccoli, leafy greens, chia/flax, nuts.

Disclaimer

For educational purposes only. Not medical or dietary advice.

References

• The Health Benefits of Dietary Fibre — Nutrition Reviews
• Current Understanding of Dietary Fiber and Its Role in Chronic Disease — PMC
• Dietary Fiber Intake and All-Cause and Cause-Specific Mortality — Clinical Nutrition (2023)
• Dietary Intake of Total Vegetables, Fruit, Cereal, Soluble and Insoluble Fibre & Mortality — Frontiers in Nutrition (2023)
• Therapeutic Benefits & Dietary Restrictions of Fiber Intake — MDPI Nutrients (2022)
• The Impact of Dietary Fiber Consumption on Human Health — Clinical Nutrition Journal (2025)
• Dietary Fibre Intake & Gut Microbiota in Human Health — PMC (2023)