Fennel is a crunchy, mildly licorice-flavored vegetable that's a surprisingly good source of dietary fiber — especially when you eat the bulb, fronds, or seeds. This fennel fiber per 100g calculator tells you exactly how many grams of fiber you're getting from any serving, based on USDA nutrient data for raw bulb, cooked bulb, leaves, and dried seeds.
Just enter your amount in grams or ounces, choose the fennel form, and hit calculate. The tool instantly shows total fiber, the fiber density per 100g, and how much of your daily fiber target that serving covers. It's handy for meal prep, low-carb or high-fiber planning, and checking whether fennel seeds really deserve their reputation as a digestive aid.
No more guessing between “a cup of sliced fennel” and “a teaspoon of seeds” — this calculator standardizes everything to per-100g values and converts it to your plate.
🥬 Fennel Fiber Calculator
Calculate fiber from fennel bulb, fronds, or seeds — based on USDA per-100g values.
How to Use This Tool
Start by entering the amount of fennel you plan to eat in the input field — you can type grams or ounces, or use a quick preset like 100 g or 1 medium bulb (234 g). Then choose the fennel form that matches your food: raw fennel bulb, cooked fennel bulb, raw leaves/fronds, or dried fennel seeds. Press Calculate fiber and you'll get three useful numbers: the total fiber in your serving, the fiber density per 100 g for that form, and how much of the standard 28 g daily fiber target the serving covers. Use the reset button to clear everything and start a new serving. This makes it easy to compare fennel to other vegetables in your diet, plan a high-fiber day, or quickly add up your fiber from a recipe that uses a handful of fennel seeds.
Fennel Fiber Reference Data
The values below come from USDA FoodData Central and represent typical fiber content for each fennel form:
| Form | Fiber per 100 g | Common serving | Fiber per serving |
|---|---|---|---|
| Raw fennel bulb | 3.1 g | 1 cup sliced (87 g) | 2.7 g |
| Cooked fennel bulb (boiled) | 2.7 g | 1 cup sliced (87 g) | 2.3 g |
| Raw fennel leaves/fronds | 2.6 g | 1 tbsp chopped (3 g) | 0.1 g |
| Dried fennel seeds | 39.8 g | 1 tbsp (5.8 g) | 2.3 g |
Notice how much more concentrated the seeds are. That's why the calculator lets you switch forms — the difference between “a cup of bulb” and “a teaspoon of seeds” is huge on a per-gram basis.
How It Works: The Calculation
The tool applies a simple proportional formula:
Fiber (g) = Amount eaten (g) × Fiber density (g per 100 g) ÷ 100
The fiber density is a constant for each form, drawn from the table above. The daily value percentage is then calculated as fiber ÷ 28 g × 100, following the FDA's general adult daily value for dietary fiber.
Why Fennel Fiber Matters
Fennel's fiber is mostly insoluble, which adds bulk to stool and helps keep things moving, plus fermentable fibers that feed beneficial gut bacteria. Key benefits include:
- Digestive health: Regular fiber intake is linked to healthier bowel habits and lower risk of constipation.
- Satiety: Fiber slows stomach emptying, so a 200 g roasted fennel side dish can make a meal feel more filling without many calories.
- Heart health: Soluble fiber in particular can help reduce blood cholesterol levels; fennel also provides potassium and vitamin C.
- Gut microbiome: Fermentable fiber in fennel supports short-chain fatty acid production, important for colon health.
Fennel seeds have long been used in traditional medicine to ease bloating, and their high fiber content is one reason they're so effective as a post-meal digestive aid. If you're comparing fiber across foods, you might also like the watercress fiber calculator for another leafy green.
Accuracy Notes & Limitations
- Natural variation: Fiber content in fennel depends on cultivar, season, soil, and maturity. USDA values are averages.
- Cooking effects: Boiling can change water content, so cooked fennel has slightly less fiber per 100 g than raw, but total fiber isn't destroyed by normal cooking.
- Seed serving sizes: Dried fennel seed weights can vary; 1 tbsp is about 5.8 g, but check your spice jar nutrition label.
- Daily target: 28 g/day is the FDA reference for adults on a 2,000-calorie diet. Individual needs vary — athletes or people on high-calorie diets may need more.
- Not medical advice: This calculator is an educational tool, not a substitute for advice from a registered dietitian.
Frequently Asked Questions
Is fennel really a high-fiber vegetable? Per 100 g, raw fennel bulb has about 3.1 g of fiber — comparable to cabbage, broccoli, and bell peppers. It's not the highest-fiber vegetable, but it's a solid contributor, and fennel seeds are exceptionally dense.
Do fennel seeds have more fiber than the bulb? Yes. Dried seeds contain roughly 13 times more fiber by weight than the raw bulb, because they're concentrated and dry. A tablespoon of seeds delivers about 2.3 g of fiber.
Does cooking fennel destroy its fiber? No. Heat doesn't break down fiber. Boiling may cause the vegetable to absorb or lose water, which slightly changes the fiber percentage per 100 g, but the total fiber in the food remains basically intact.
Are fennel fronds usable for fiber? Yes. Chopped fronds have a similar per-100g fiber count to the bulb, although they're usually eaten in small amounts. If you toss a handful into salads or soups, every little bit counts.
Can I count fennel tea as fiber? No — brewing fennel seeds in hot water extracts flavor and some water-soluble compounds, but the insoluble fiber stays in the seeds unless you consume the grounds. The calculator assumes you're eating the fennel, not just drinking tea.
For more on how different foods compare per 100 grams, see the bread fiber calculator or read the Mayo Clinic's guide to dietary fiber.