FiberUp
How much fiber is in onion?
Onion has 1.9 g of fiber per 1 medium (110 g). That is 7% of the daily value and a moderate amount for an vegetable.
Soluble vs insoluble
The split is approximate and comes from USDA SR Legacy analyses where available. Soluble fiber dissolves into a gel and is the type most linked to cholesterol and blood sugar effects. Insoluble fiber adds bulk and keeps things moving.
About onion and fiber
A medium onion has 1.9 grams of fiber, and because onions are cooked into so many dishes they add up across the day. They are high FODMAP from fructans, one of the most common triggers on that plan.
How onion compares to other vegetables
Per typical serving. The highest vegetable in the database is artichoke at 6.9 g.
| Food | Serving | Fiber | Per 100 g | % DV |
|---|---|---|---|---|
| Romaine Lettuce | 2 cups | 2 g | 2.1 g | 7% |
| Zucchini | 1 medium | 2 g | 1 g | 7% |
| Bean Sprouts | 1 cup | 1.9 g | 1.8 g | 7% |
| Onion | 1 medium | 1.9 g | 1.7 g | 7% |
| Cherry Tomatoes | 1 cup | 1.8 g | 1.2 g | 6% |
| Hearts of Palm | 1/2 cup | 1.8 g | 2.5 g | 6% |
| Peeled Potato | 1 medium | 1.8 g | 1.3 g | 6% |
Servings to reach a daily goal
servings of onion to reach 25 g, the adequate intake for adult women
servings of onion to reach 38 g, the adequate intake for adult men
Nobody should get all their fiber from one food. Gut bacteria respond to variety, and the fiber calculator shows a mixed day that reaches your number.
USDA entries for onion
Grams of fiber per 100 g from USDA FoodData Central (snapshot 2026-10-11). Different preparations and varieties explain the spread.
| USDA description | Fiber / 100 g | Soluble | Insoluble |
|---|---|---|---|
| Onions, red, raw | 2.2 g | – | – |
| Onions, white, raw | 1.2 g | – | – |
| Onions, yellow, raw | 1.9 g | – | – |
| Onions, raw | 1.7 g | – | – |
| Onions, sweet, raw | 0.9 g | – | – |
| Onions, welsh, raw | 2.4 g | – | – |
| Onions, spring or scallions (includes tops and bulb), raw | 2.6 g | – | – |
| Onions, yellow, sauteed | 1.7 g | – | – |
Frequently asked questions
How much fiber is in onion?
Is onion high in fiber?
Is the fiber in onion soluble or insoluble?
How many servings of onion would reach a daily fiber goal?
Values are per typical serving from USDA FoodData Central and standard references, rounded to one decimal. Actual fiber varies with variety, ripeness, and preparation. This is general nutrition information, not medical advice.