How many calories in a whole yellow onion?

Onions are a common vegetable found in many cuisines around the world. Their versatility in cooking comes from their unique combination of flavors and textures. When raw, onions have a sharp, pungent taste that mellows out when they are cooked. They can be eaten raw, cooked, fried, grilled, baked, or caramelized.

Yellow onions specifically provide a bright, sweet flavor that balances out recipes. They are larger and have a higher water content than other onion varieties. Their papery outer skins range in color from yellow to brown. Underneath lies a series of concentric rings in hues of purple or white.

Quick Answer

A whole medium yellow onion contains around 44 calories.

Calories and Nutrients in Onions

The calorie and nutrient content of onions can vary depending on the specific size and variety. Here are some of the key details about the nutritional profile of yellow onions:

  • One medium yellow onion (approx. 110g) provides 44 calories.
  • Yellow onions are very low in fat and contain 0.1g of fat per medium onion.
  • They contain no cholesterol.
  • There are 10g of carbohydrate in a medium onion, including 4g of dietary fiber and 5g of sugars.
  • Onions are a good source of vitamin C, with one medium onion containing 12mg.
  • They also contain small amounts of folate, vitamin B6, potassium, and manganese.

The calories in onions primarily come from their carbohydrate content. Onions get most of their calories from complex carbohydrates and natural sugars. Raw onions contain fructans, which are soluble fibers linked to health benefits. When onions are cooked, these fructans break down into fructose, glucose, and other sugars.

Onion Calories by Type and Serving Size

Calories in onions can vary somewhat depending on the specific type and serving size. Here is the nutrition breakdown for some common onion types and serving sizes:

Onion Type Serving Size Calories
Yellow onion 1 small (70g) 31 calories
Yellow onion 1 medium (110g) 44 calories
Yellow onion 1 large (175g) 72 calories
White onion 1 medium (110g) 44 calories
Red onion 1 medium (110g) 46 calories
Sweet onion 1 medium (110g) 44 calories

As shown, the number of calories in an onion serving increases progressively from small to large onions. There is little difference in calories between yellow, white, red, and sweet onions for comparable serving sizes.

Calories in Raw vs Cooked Onions

Cooking onions can change their nutritional profile and calorie content. Here is how raw and cooked onions compare:

  • Raw onions are very low in calories and fat.
  • Cooking onions reduces the amount of sulfur compounds, intensifying their sweetness.
  • Cooked onions have more available carbohydrates and sugars than raw.
  • Frying adds significant calories from oil. Deep-fried onion rings can have 150 or more calories per serving.
  • Caramelizing onions adds natural sugars, with around 50 calories in 1⁄4 cup caramelized onion.
  • Overall, cooked onions will have slightly more calories per serving than raw.

Calories in Onion Powder and Flakes

Dehydrated onion products like onion powder and flakes are very low in calories. Here is how they compare:

  • 1 tablespoon onion powder: 12 calories
  • 1 tablespoon onion flakes: 10 calories
  • Onion powder and flakes retain onions’ natural sugars and fiber but lose their water content.
  • This concentrates the flavor so you use less. Measured by volume, they contain far fewer calories than fresh onions.

Ways to Reduce Onion Calories

For most recipes, onion calories are negligible considering the small serving size. But for certain diets or recipes, you may want to reduce onion calories even further. Here are some options:

  • Use minimal added fat when cooking onions.
  • Opt for raw onions instead of fried.
  • Substitute onion powder or flakes in place of some fresh onion.
  • Sauté in broth or water instead of oil.
  • Skip deep-frying onion rings; bake or air-fry instead.
  • Choose smaller onions which have fewer calories per serving.

Typical Onion Uses and Calorie Counts

To estimate how many calories onions add to your recipe or meal, it helps to be aware of typical serving sizes and cooking methods. Here are some common ways onions are used and the approximate calorie counts:

Onion Use Serving Size Calories
Chopped raw onion in salad 2 Tbsp (20g) 8 calories
Sautéed onions 1⁄4 cup (40g) 16 calories
Onion soup 1 cup 50 calories
Onion rings, air fried 8 rings (72g) 29 calories
Caramelized onions 1⁄4 cup 50 calories

As you can see, typical serving sizes of onions add minimal calories to recipes and dishes. Even large amounts like in onion soup equate to just 50 calories.

Onion Calories Compared to Other Vegetables

Like most non-starchy vegetables, onions are very low in calories for their serving size. How do they compare to other common veggies?

For reference, one medium onion (110g) contains 44 calories. That’s less than or comparable to many other raw vegetables:

  • Broccoli florets: 31 calories in 100g
  • Baby carrots: 35 calories in 100g
  • Tomato: 18 calories in 100g
  • Cucumber: 15 calories in 100g
  • Bell pepper: 20 calories in 100g

Overall, onions fit into a healthy, low-calorie diet, similarly to other non-starchy vegetables.

Onions for Weight Loss

Adding more onions to your diet can support weight loss in a few ways:

  • Low calorie – Onions are very low in calories, so you can eat larger portions to feel full.
  • High in fiber – The fiber content helps you feel satisfied.
  • Provide volume – Their crunchy, juicy texture adds bulk to dishes.
  • Flavor enhancement – Onions make foods taste better with minimal calories added.
  • Anti-inflammatory – Compounds may help reduce inflammation linked to obesity.

Enjoy onions freely as part of a healthy, low-calorie way of eating for weight management.

Health Benefits of Onions

Besides being low in calories, onions provide many other nutrients and health benefits. Some of the top benefits include:

  • Immune function – Contain anti-bacterial and anti-viral components.
  • Cancer prevention – Rich in flavonoids with antioxidant and anti-cancer properties.
  • Heart health – Sulfur compounds may lower blood pressure and cholesterol.
  • Blood sugar control – Have compounds that may lower blood sugar levels.
  • Gut health – Provide prebiotics to support healthy gut bacteria.
  • Strong bones – Small amounts of manganese promote bone formation.

Be sure to keep the skin on onions to maximize their nutrient and fiber content.

Tips for Cooking with Onions

Here are some tips for preparing onions while keeping calories low:

  • Opt for minimal added oils when cooking onions. Use broth or water instead.
  • Cut onions 5-10 minutes before cooking to maximize their anti-inflammatory benefits.
  • Cook onions thoroughly to reduce their pungency and bring out their natural sweetness.
  • Save leftover cooked onions in the fridge for a few days. Add to salads, sandwiches, omelets or anywhere you want extra flavor.
  • Blend cooked onions into dips, spreads, dressings, and sauces.
  • Top baked potatoes, tacos, pizza, and flatbreads with caramelized onions.

Simple Low-Calorie Onion Recipes

Here are a few easy, low-calorie onion recipes:

Caramelized Onion Hummus

Blend chickpeas, tahini, caramelized onions, garlic, lemon juice, and seasonings for a flavor-packed hummus dip.

Veggie Quiche with Onion and Tomato

Bake eggs with onion, tomato, spinach, and feta cheese in a savory crust for a protein-packed brunch.

Baked Onion Rings

Toss sliced onions in a little oil and breadcrumbs. Bake at 400F until browned and crispy outside while tender inside.

Chicken Fajitas

Sauté sliced bell peppers and onions, serve in tortillas or over greens with grilled chicken seasoned with cumin and chili powder.


To summarize the key points:

  • One medium yellow onion contains around 44 calories.
  • Calories come mostly from natural carbohydrates and sugars.
  • Cooking can increase the available carbohydrates and sugars in onions.
  • Typical serving sizes of onions add minimal calories to dishes.
  • Onions are very low-calorie compared to most other vegetables.
  • Eating more onions may aid weight loss through multiple mechanisms.
  • Onions provide many beneficial nutrients and antioxidants.

Overall, onions are an excellent low-calorie vegetable that provides significant nutritional value. Add more onions to your recipes to enhance flavor and nutrition without worrying about too many calories.

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