Fennel is a crisp, aromatic vegetable that adds big flavor without packing in calories. This calculator estimates the calories, macronutrients, fiber, and key vitamins in any amount of raw fennel bulb, whether you weigh it in grams, measure it in cups, or use an entire medium bulb. It is useful for meal prep, low-carb and keto planning, and anyone tracking micronutrients such as potassium, vitamin C, and vitamin K.
The nutrition values are based on USDA FoodData Central entries for raw fennel bulb and scale automatically with the serving size you enter. Toggle the detailed micronutrients panel to see potassium, vitamin C, vitamin K, and folate alongside the macros. Use the quick-fill buttons for a 100 g serving or a typical cup of sliced fennel, then click Calculate for a clean breakdown that helps you log meals and hit daily nutrition targets.
🥬 Fennel Nutrition Calculator
Estimate calories, macronutrients, fiber, net carbs, and key micronutrients in raw fennel bulb.
Step-by-Step Guide
Using the calculator is quick. Start by entering the amount of raw fennel bulb you plan to eat, then choose the matching unit from the dropdown: grams, ounces, cups of sliced fennel, or a whole medium bulb. The quick-fill buttons auto-enter a 100 g serving, a 1-cup serving (87 g), or one medium bulb (about 235 g). Keep the micronutrient toggle on if you want vitamin K, vitamin C, potassium, and folate included in the results. Click Calculate Nutrition to see calories, protein, carbohydrates, fat, fiber, net carbs, sugars, and the optional micronutrient cards. If you type an invalid or non-positive number, the calculator displays an error in the result area. Reset returns everything to a 100 g default.
The result layout is designed for easy logging. The large blue number is total calories for your exact serving. Below it are three macro cards: protein, total carbohydrate, and fat. The next row separates fiber, net carbs, and sugars, which is especially useful for low-carb and ketogenic meal planning. Net carbs are simply total carbohydrate minus fiber, so fennel delivers a reasonable amount of carbohydrate while still contributing useful fiber. If the micronutrient toggle is on, four additional cards show potassium, vitamin C, vitamin K, and folate. A final calculation-steps box explains how the serving weight and scale factor were derived from your input.
Calculation Method
This calculator uses per-100-gram nutrient values for raw fennel bulb from USDA FoodData Central. The math has three steps. First, convert the entered amount to grams: grams = amount × unit factor. For example, if the unit is ounces, the unit factor is 28.3495 g per ounce. Second, divide that gram weight by 100 to get a scale factor. Third, multiply every per-100g value by the scale factor. The formula is nutrient value = USDA per-100g value × (serving weight in grams / 100). This linear scaling works because the calculator is designed for raw bulb only; cooking changes water content and can alter nutrient density.
Worked Examples
Here are two typical servings to show how the numbers move.
Tips & Common Mistakes
Fennel bulbs vary in size, so use the whole-bulb option as an estimate. The medium bulb figure of about 235 g is a convenient midpoint, but a large bulb with thick outer layers can be 300 g or more. For the most accurate food logging, weigh the trimmed edible portion on a kitchen scale and enter grams directly.
Do not confuse bulb servings with fennel seeds or fennel fronds. Dried fennel seeds are far more calorie-dense per gram and have a different fat and fiber profile. The fronds are edible and aromatic, but their nutrient values are not the same as the bulb, so keep them out of the serving weight if you are using this calculator. Cooking also matters: roasted or sautéed fennel loses water, which concentrates calories per gram even though the total nutrients in the pan stay similar.
Reference Table
Approximate USDA values for raw fennel bulb per 100 g:
| Nutrient | Per 100 g |
|---|---|
| Calories | 31 kcal |
| Protein | 1.24 g |
| Total fat | 0.20 g |
| Carbohydrate | 7.30 g |
| Fiber | 3.10 g |
| Sugars | 3.92 g |
| Potassium | 414 mg |
| Sodium | 52 mg |
| Vitamin C | 12.0 mg |
| Folate | 27 µg |
| Vitamin K | 62.8 µg |
| Iron | 0.73 mg |
Frequently Asked Questions
Is fennel low in carbs? A 100 g serving of raw fennel bulb has about 7.3 g of total carbohydrate and 3.1 g of fiber, so net carbs are about 4.2 g. That makes it a friendly vegetable for moderate low-carb diets, though portion size still matters.
Is the calculator suitable for cooked fennel? No. The values assume raw fennel bulb. Cooking removes water and can change nutrient concentrations, so weigh cooked fennel separately.
What is the difference between fennel bulb, fronds, and seeds? The bulb is the crunchy white-to-pale-green base used as a vegetable. Fronds are the feathery leaves, and the seeds are a spice. While all come from fennel (Foeniculum vulgare), their nutrition differs significantly. This calculator is for the raw bulb only.
Which micronutrients are most notable in fennel? Fennel is especially rich in vitamin K, potassium, and vitamin C relative to its calorie count. A 100 g serving provides roughly 62.8 µg of vitamin K, 414 mg of potassium, and 12 mg of vitamin C. For a closer look at iron, use the dedicated fennel iron calculator.