Calories in Onion
Onions contain 40 kcal per 100g raw and 44 kcal cooked. A medium onion is about 44 kcal — fundamental to cooking but small calorie contribution.
Nutrition by portion size
| Portion | kcal | Carbs (g) | Protein (g) | Fat (g) | Fiber (g) |
|---|---|---|---|---|---|
| 1 medium onion (~110g) | 44 | 10 | 1.2 | 0.1 | 1.8 |
| 1 cup chopped onion (~160g) | 64 | 15 | 1.8 | 0.2 | 2.7 |
| 100g raw onion | 40 | 9 | 1.1 | 0.1 | 1.7 |
| 100g caramelized onion | 60 | 13 | 1.5 | 0.5 | 2.5 |
| 100g fried onion rings | 410 | 38 | 5 | 27 | 1.5 |
About these numbers
Onions are cooking foundations — providing flavor and modest nutrition (vitamin C, quercetin, fiber) for minimal calorie cost. A medium onion is 44 kcal raw, ~60 kcal cooked. Fried onion rings are the calorie disaster — 410 kcal per 100g (10x the raw onion).
Use the calculators
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- Net Carbs Calculator — useful for keto and T1D insulin dosing
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Frequently asked questions
- How many calories in an onion?
- Medium onion: 44 kcal raw. Per cup chopped: 64 kcal. Cooked is slightly higher due to oil typically used. Fried onion rings: 410 kcal per 100g — major calorie difference.
- Are onions good for weight loss?
- Yes — low calorie, high flavor density. A medium onion adds 44 kcal to a meal while transforming flavor. For calorie-conscious cooking, onions are valuable as flavor base without significant calorie load.
- Are onions healthy?
- Yes. Provide vitamin C, B6, folate, plus quercetin (antioxidant linked to cardiovascular benefit). The 2019 Pellegrino et al. analysis found regular onion consumption was associated with reduced cardiovascular events. Practical daily inclusion in cooking is unambiguously beneficial.
- Red onion vs yellow onion?
- Red onions have more anthocyanins (antioxidants); yellow have more pungent flavor when cooked. Both are nutritious. For salads and salsas, red is sweeter raw. For cooking, yellow caramelizes better. Choose by recipe preference.
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