Quick Answer: Calories in Onion
There are approximately 38 calories in 100 grams of onion. This page gives you a full nutrition-style breakdown for calories, carbs, net carbs, protein, fat, fiber, vitamins, minerals, and diet compatibility.
Onion Nutrition Facts Per 100g
| Nutrient | Amount per 100g |
|---|---|
| Calories | 38 kcal |
| Total carbs | 7.4g |
| Net carbs | 4.5g |
| Fiber | 3.0g |
| Protein | 1.8g |
| Fat | 0.4g |
Is Onion Keto Friendly?
Keto friendly: Yes. With about 4.5g net carbs per 100g, it can usually fit into a keto day when portions are controlled. If you are using a ketogenic diet for fat loss, blood sugar control, or appetite control, always compare this food with your personal daily carb target.
Read the focused keto page here: Is onion keto?
Is Onion Low Carb?
Low-carb friendly: Yes. It is generally low-carb friendly in normal portions. For a low-carb lifestyle, the most important detail is not only calories, but how the food fits into the full day of meals.
Read the focused low-carb page here: Is onion low carb?
Is Onion Paleo Friendly?
Paleo friendly: Yes. It is generally paleo friendly because it is a whole-food ingredient or minimally processed food.
Vitamins in Onion
Onion may provide vitamin C, vitamin K, folate, and small amounts of B vitamins. The exact vitamin profile can change depending on freshness, cooking method, fortification, recipe, and serving size.
Minerals in Onion
Important minerals commonly associated with this food category include potassium, magnesium, calcium, iron, and manganese. Minerals are one reason it is helpful to look beyond calories alone when building a healthy meal.
What Is Onion Considered Healthy For?
Onion can support a balanced diet when it matches your calories, protein needs, carb tolerance, and meal timing. In practical terms, this food may help with energy, satiety, micronutrient intake, or recipe variety. The best use depends on your goal: weight loss, maintenance, muscle tone, low-carb eating, or a higher-energy workout day.
How to Combine Onion in a Low-Carb Diet
1. Pair it with protein
Use a small portion of onion with eggs, Greek yogurt, chicken, tuna, turkey, tofu, or another protein source. Protein helps make the meal more filling.
2. Add low-carb volume
Combine it with cucumber, lettuce, spinach, zucchini, broccoli, cauliflower rice, mushrooms, or a big salad to keep the plate larger without pushing carbs too high.
3. Use fat strategically
Add avocado, olive oil, cheese, nuts, seeds, or a creamy dressing if it fits your plan. Fat can improve fullness, but it also adds calories quickly.
Calories vs Carbs: What Matters More?
For weight loss, calories still matter. For keto and low-carb eating, carbs and net carbs matter too. The most useful approach is to track both: calories for the energy balance and net carbs for how the food fits your low-carb target.
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Note: Nutrition values are approximate per 100g and can vary by brand, recipe, ripeness, cooking method, and database source. Use this guide as a practical reference, not medical advice.