How many carbs are in an onion?
A medium raw onion has about 10g of carbohydrate and 8g of net carbs. Onions carry more natural sugar than most aromatics, though you rarely eat a whole one.
Carbs by portion
| Portion | Total carbs | Fiber | Net carbs |
|---|---|---|---|
| 1 medium onion (110g) | 10.3g | 1.9g | 8.4g |
| 1 small (70g) | 6.5g | 1.2g | 5.3g |
| 1 large (150g) | 14.0g | 2.5g | 11.5g |
| 1 cup, chopped (160g) | 14.9g | 2.7g | 12.2g |
| 100 grams | 9.3g | 1.7g | 7.6g |
Net carbs
A medium onion has about 8g of net carbs, which is total carbs (10g) minus fiber (2g). Most recipes use far less than a whole onion, so the carbs per serving are usually small. See the net carbs guide.
For diabetes
A whole onion is about 10g of carbohydrate, but a few slices or a spoonful of chopped onion is negligible. Count it when onion is the bulk of a dish, such as onion rings or a big pile of caramelized onions. See the diabetes carb-counting guide.
Keto and low carb
In small amounts. A spoonful of chopped onion as a flavor base fits easily, but half a cup of chopped onion is about 4g net carbs and adds up. Use onion to season, not as a bulk vegetable, on keto.
Good to know
Onions taste sweet because they hold more natural sugar than garlic or scallions. Caramelizing concentrates that sugar as the water cooks off, so a spoonful of caramelized onion has more carbs than a spoonful of raw. Onion powder is concentrated too, so it counts faster than it looks.
Full nutrition (per 100g)
- Calories: 40.0 kcal
- Carbohydrate: 9.34g
- Fiber: 1.7g
- Sugars: 4.24g
- Protein: 1.1g
- Fat: 0.1g
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Get the appFrequently asked questions
How many carbs are in an onion?
A medium raw onion has about 10g of carbohydrate. Half a cup chopped is about 5g.
How many net carbs are in an onion?
A medium onion has about 8g of net carbs, total carbs (10g) minus about 2g of fiber.
Are onions OK for diabetics?
Yes, in normal cooking amounts. A few slices barely register. Count onions when they are the main part of a dish, like onion rings.
Are onions keto?
In small amounts. Onion works as a flavor base, but half a cup of chopped onion is about 4g net carbs, so it can eat into a tight keto budget.
Do caramelized onions have more carbs?
Per spoonful, yes. Caramelizing cooks off the water and concentrates the natural sugar, so caramelized onions are denser in carbs than raw.