Yellow Onion Calories: Exact Count Per Serving (2025 Data)

A medium yellow onion (110g) contains approximately 44 calories, with 10 calories per 1/4 cup chopped. This comprehensive guide breaks down the exact nutritional profile, compares varieties, and shows how yellow onions fit into healthy eating plans.

When tracking your daily nutrition, knowing the precise calorie count of common ingredients like yellow onions is essential for accurate meal planning. Whether you're managing dietary goals, counting macros, or simply curious about this kitchen staple, understanding the nutritional facts helps you make informed cooking decisions.

Nutritional Breakdown of Yellow Onions

According to the USDA FoodData Central database, yellow onions offer a remarkably low-calorie profile while delivering valuable nutrients. The exact count depends on serving size, but here's what the numbers reveal:

Serving Size	Calories	Carbohydrates (g)	Fiber (g)	Sugar (g)
100g raw yellow onion	40	9.3	1.7	4.2
Medium onion (110g)	44	10.2	1.9	4.6
1/4 cup chopped (40g)	16	3.7	0.7	1.7
1 cup chopped (160g)	64	14.9	2.7	6.8

This nutritional profile comes from the USDA's most recent analysis of raw yellow onions (Allium cepa), the most commonly used variety in American kitchens. The data reflects onions in their raw state, as cooking methods can slightly alter nutritional values through water loss or caramelization processes.

How Yellow Onions Compare to Other Varieties

Not all onions are nutritionally identical. While calorie counts remain relatively consistent across varieties, subtle differences exist in sugar content and nutrient density:

• Yellow onions: 40 calories per 100g, higher sulfur compounds (more pungent, better for cooking)
• Red onions: 40 calories per 100g, contain anthocyanins (antioxidants giving purple color)
• White onions: 42 calories per 100g, milder flavor, slightly higher water content
• Shallots: 72 calories per 100g, more concentrated flavor and nutrients
• Green onions: 32 calories per 100g, lower carbohydrate content

These comparisons come from side-by-side analysis in the USDA FoodData Central, which maintains standardized testing protocols for consistent nutritional reporting across produce varieties.

Practical Calorie Management in Cooking

Understanding how yellow onions contribute to your meal's total calorie count helps with precise dietary planning. Consider these real-world applications:

When sautéing onions for a recipe serving four people, using one medium yellow onion (44 calories total) adds just 11 calories per serving. This makes them an excellent flavor foundation without significant caloric impact. For those following specific dietary patterns:

• Keto diets: Yellow onions contain 9g net carbs per 100g, so moderate portions fit within daily limits
• Diabetes management: The 1.7g fiber per 100g helps moderate blood sugar response to carbohydrates
• Weight loss: Their strong flavor allows using smaller quantities while still enhancing dishes

Professional chefs often recommend reserving sweeter varieties like Vidalia for raw applications while using yellow onions for cooking, as their higher sulfur content creates richer flavor compounds when heated without adding significant calories.

Beyond Calories: Nutritional Benefits of Yellow Onions

While the calorie count matters for dietary tracking, yellow onions offer valuable nutritional components beyond their energy content:

• Vitamin C: 7.4mg per 100g (8% of daily value) - supports immune function
• Vitamin B6: 0.12mg per 100g (7% of daily value) - aids metabolism
• Manganese: 0.13mg per 100g (6% of daily value) - important for bone health
• Quercetin: A flavonoid antioxidant with anti-inflammatory properties
• Organosulfur compounds: May support cardiovascular health

Research published in the Journal of Nutrition and Metabolism indicates that regular onion consumption correlates with improved cardiovascular markers, demonstrating that the nutritional value extends far beyond the modest calorie count.

Maximizing Nutritional Value in Preparation

How you prepare yellow onions affects their nutritional profile. To preserve maximum nutrients while managing calories:

• Store whole onions in a cool, dry place (not the refrigerator) to maintain nutrient density
• Leave the outer layers intact until ready to use - they contain concentrated antioxidants
• Chop and wait 10 minutes before cooking to activate beneficial enzymes
• Avoid overcooking, which can degrade heat-sensitive vitamins
• Use minimal oil when sautéing to prevent unnecessary calorie addition

These preparation techniques help maintain the natural nutritional benefits while keeping the calorie count predictable for dietary tracking purposes.

Common Questions About Onion Nutrition

Many home cooks have specific questions about incorporating yellow onions into their nutrition plans. Here are answers to the most frequent inquiries:

Do cooked yellow onions have more calories than raw?

Cooked yellow onions have slightly more calories per gram than raw due to water loss during cooking, but the total calories in the entire onion remain the same. A medium cooked onion still contains approximately 44 calories total.

Are yellow onions suitable for low-carb diets?

Yellow onions contain about 9g net carbs per 100g, so they can fit into moderate low-carb diets when portion-controlled. For stricter keto diets (under 20g net carbs daily), limit to 1/4 cup chopped (about 3.7g net carbs) per serving.

How do yellow onions compare to sweet onions nutritionally?

Yellow onions contain slightly fewer calories (40 vs 43 per 100g) and less sugar (4.2g vs 5g per 100g) than sweet varieties like Vidalia. Both offer similar fiber and vitamin content, but yellow onions have higher sulfur compounds which create more complex flavors when cooked.

Does the calorie count change when caramelizing onions?

The total calories remain the same when caramelizing onions, but the concentration increases as water evaporates. One cup of raw chopped onions (64 calories) reduces to about 1/4 cup caramelized (still 64 calories), making the calorie density higher in the final product.