Onion Calories: Exact Count Per Serving (2024 Data)

A medium-sized onion (approximately 110 grams) contains 44 calories. This precise nutritional information comes directly from the USDA FoodData Central database, the most authoritative source for food nutrition facts in the United States.

Understanding the exact calorie content of common ingredients like onions is essential for meal planning, dietary tracking, and maintaining a balanced diet. Whether you're counting calories for weight management or simply curious about your food's nutritional profile, having accurate information matters.

Breaking Down Onion Calories by Type and Size

Not all onions are created equal when it comes to calorie content. The specific variety, size, and preparation method all affect the final count. Let's examine the nutritional differences across common onion types.

Onion Type	Standard Serving Size	Calories	Carbohydrates (g)	Fiber (g)
Yellow Onion (medium)	110g	44	10.3	1.9
Red Onion (medium)	110g	42	9.9	1.8
White Onion (medium)	110g	43	10.1	1.9
Green Onions (scallions)	100g	32	7.3	2.6
Shallot	100g	72	16.8	3.2

This nutritional comparison, sourced from the USDA FoodData Central, shows that while yellow, red, and white onions have nearly identical calorie counts, shallots contain significantly more calories per 100 grams. Green onions (scallions) are the lowest in calories among common onion varieties.

Understanding Onion Nutrition Beyond Calories

While calorie count is important for many people tracking their food intake, onions offer valuable nutritional benefits that extend far beyond their modest energy content:

• Vitamin C: One medium onion provides about 11% of your daily recommended intake
• B vitamins: Particularly B6 and folate, essential for energy metabolism
• Antioxidants: Onions contain quercetin, a powerful flavonoid with anti-inflammatory properties
• Fiber: Approximately 1.9 grams per medium onion, supporting digestive health
• Minerals: Contains small amounts of potassium, manganese, and calcium

Practical Applications: Using Onion Calories in Meal Planning

Knowing the exact calorie content of onions helps you make informed decisions in your kitchen. Here's how to apply this information practically:

For Weight Management

Onions are an excellent addition to calorie-conscious meals. Their strong flavor means you can use less oil or high-calorie seasonings while still creating delicious dishes. A medium onion adds only 44 calories to your recipe while significantly enhancing flavor.

For Blood Sugar Management

With a glycemic load of just 2 for a medium onion, they're suitable for most blood sugar management plans. The fiber content (1.9g per medium onion) helps slow glucose absorption.

Context Boundaries: When Onion Calories Might Vary

Certain preparation methods can significantly alter the calorie content of onions:

• Fried onions: A 1/4 cup of crispy fried onions contains approximately 90 calories due to oil absorption
• Caramelized onions: The natural sugars concentrate during cooking, increasing calories per volume (about 70 calories per 1/2 cup)
• Onion rings: A typical serving (85g) can contain 250-300 calories depending on batter and frying method

These variations demonstrate why understanding preparation methods is crucial when tracking calories accurately. The raw onion values provided earlier apply specifically to uncooked onions.

Common Misconceptions About Onion Calories

Several myths persist about onion nutrition that deserve clarification:

• "Onions are high in sugar": While onions do contain natural sugars (about 4.7g per medium onion), this is comparable to many non-starchy vegetables and comes with fiber that moderates blood sugar impact
• "Cooking removes all nutritional value": While some heat-sensitive nutrients decrease, cooking actually increases the bioavailability of certain antioxidants like quercetin
• "All onion varieties have identical nutrition": As shown in our comparison table, shallots contain nearly twice the calories of other common onion types per 100g

How Onions Fit Into a Balanced Diet

With their low calorie count and rich nutrient profile, onions are a valuable component of most dietary patterns. Whether you're following Mediterranean, DASH, or plant-based eating approaches, onions provide flavor without excessive calories.

Professional chefs often use the "sofrito" technique—sautéing onions, garlic, and other aromatics as a flavor base—which maximizes taste while keeping overall calorie counts in check. This professional approach demonstrates how understanding ingredient nutrition helps create satisfying meals within calorie goals.

How many calories are in a small onion?

A small onion (about 80 grams) contains approximately 32 calories according to USDA data.

Do cooked onions have more calories than raw onions?

The calorie count remains the same when onions are simply cooked without added ingredients. However, caramelized onions have slightly higher calories per volume due to water loss, and fried onions absorb oil, significantly increasing their calorie content.

Are onions good for weight loss?

Yes, onions are excellent for weight loss diets. With only 44 calories for a medium onion, they add significant flavor and volume to meals without many calories. Their fiber content also promotes feelings of fullness.

How many carbs are in an onion?

A medium onion (110g) contains approximately 10.3 grams of carbohydrates, including 1.9 grams of dietary fiber.