How many calories are in 65 g of red onion?

November 27, 2025 •

3 min read

According to nutrition data, a typical 65-gram serving of raw red onion contains approximately 26 to 27 calories. This low-calorie vegetable is an excellent way to add flavor and nutrients to your meals without significantly impacting your daily calorie intake, making it a great addition for those managing their weight.

Quick Summary

A 65-gram serving of raw red onion provides about 26 to 27 calories, primarily from carbohydrates and fiber. The total macronutrient and micronutrient content is low, but it offers valuable vitamins, minerals, and antioxidants.

Key Points

Low Calorie: A 65g serving of raw red onion contains only about 26 to 27 calories.
Nutrient-Dense: Despite being low in calories, red onions are rich in vitamins, fiber, and potent antioxidants like quercetin and anthocyanins.
Health Benefits: The antioxidants in red onions are linked to improved heart health, better blood sugar regulation, and increased bone density.
Cooking Affects Density: Cooking onions removes water, which concentrates the calories per gram but does not add calories unless you use oil.
Versatile Ingredient: Raw or cooked, red onions can be added to salads, sandwiches, and many cooked dishes to enhance flavor with minimal calories.
Antioxidant Power: Red onions contain more antioxidants than white onions, making them a more powerful choice for health-conscious individuals.

The Calorie Count of 65g of Red Onion

For a health-conscious individual tracking their intake, knowing the precise nutritional value of ingredients is essential. A standard 65-gram portion of raw red onion contains around 26 to 27 calories, with some variations depending on the exact source and growing conditions. This means a small to medium-sized onion provides a minimal amount of energy, making it an ideal component for salads, sandwiches, and cooked dishes. The calorie density is very low, clocking in at approximately 40 calories per 100 grams.

To put this into perspective, 65g is roughly the size of one small onion or a handful of chopped onion. The energy provided comes almost entirely from carbohydrates, with a negligible amount from fat and protein, reinforcing its status as a light and healthy food. It's a fundamental understanding that raw vegetables are generally low in calories and red onions are no exception.

A Deeper Look at Red Onion Nutrition

Beyond just the calorie count, red onions are packed with beneficial nutrients. A 100-gram serving, slightly larger than our 65g portion, offers a clear picture of its overall nutritional profile:

Carbohydrates: Approximately 9.3 grams, with a good portion of this being natural sugars and fiber.
Fiber: Around 1.7 grams, which is important for digestive health.
Vitamins: Rich in vitamin C, which supports immune function, and B vitamins like folate and B6, which are crucial for metabolism and cell growth.
Minerals: Contains potassium, vital for fluid balance and nerve function, along with small amounts of iron and calcium.

The Role of Antioxidants

Red onions get their distinct color from anthocyanins, powerful antioxidants that have been linked to a reduced risk of heart disease. They are also one of the richest dietary sources of quercetin, a flavonoid antioxidant that may help lower blood pressure and protect against cancer. Cooking can, however, reduce the levels of some of these heat-sensitive antioxidants.

Raw vs. Cooked: How Preparation Affects Calories

When considering how many calories are in 65 g of red onion, it's crucial to understand how cooking alters its nutritional density. Cooking onions removes water, causing the weight to decrease and concentrating the nutrients and calories. Therefore, while the total calorie count of the original onion doesn't change, the calories per gram or per cup can increase.

For example, if you sauté 65g of red onion without adding any oil or butter, you might end up with a smaller, lighter pile of onion that still contains the same 26-27 calories. However, if you add oil, which contains 9 calories per gram, the total calorie count of the dish will increase significantly. A key tip is to use cooking methods like sautéing in a splash of water or broth to keep the calorie count low.

Nutritional Comparison: Raw Red Onion vs. Cooked Red Onion


Nutrient	Raw Red Onion (65g)	Cooked Red Onion (65g raw, cooked with oil)
Calories	~26-27 kcal	Varies depending on oil used. 26-27 kcal + calories from oil.
Carbohydrates	~6g	~6g (concentrated)
Fat	Negligible (~0.1g)	Significantly higher, based on the amount of added oil.
Fiber	~1g	~1g (concentrated)
Antioxidants	Higher levels (Anthocyanins, Quercetin)	Levels may be reduced due to heat

Incorporating Red Onions into Your Healthy Diet

There are numerous ways to enjoy red onions and their minimal calorie impact. For a healthy diet, consider these simple suggestions:

In salads: Thinly sliced red onion adds a sharp, crisp flavor and vibrant color to any salad.
In sandwiches and wraps: A few rings can provide a fantastic crunch and tangy bite without extra calories.
As a garnish: Finely diced red onion can top soups, tacos, and grilled meats.
Pickled: Quickly pickled red onions are a delicious, low-calorie condiment that adds a zesty flavor.
In salsas: Combine with tomatoes, cilantro, and jalapeños for a fresh, homemade salsa. To learn more about the broader benefits of onions, consider reading reliable nutritional sources such as the information provided by Healthline.

Conclusion

To conclude, a 65 g serving of raw red onion is an extremely low-calorie ingredient, providing approximately 26 to 27 calories. Its caloric impact is minimal compared to its rich flavor and nutritional value, which includes antioxidants, vitamins, and fiber. Whether you consume it raw for maximum antioxidant benefits or cook it carefully to avoid adding excess fat, red onion is a beneficial and flavorful addition to any meal plan, especially for those monitoring their calorie intake.

Frequently Asked Questions

A small red onion, which typically weighs around 65g, contains approximately 26 to 27 calories. A slightly smaller or larger onion will have a proportionally different calorie count.

Cooking red onions does not inherently increase their calorie count. However, if you cook them with oil or butter, you will add calories from the fat. Cooking primarily removes water, which concentrates the original calories into a smaller weight.

Yes, red onions are good for weight loss. They are very low in calories and fat while providing flavor, fiber, and nutrients. Including them in meals can make you feel fuller without consuming excess calories.

A 65g serving of raw red onion contains approximately 6 grams of carbohydrates, which includes both sugars and dietary fiber.

Yes, red onions offer many health benefits. They are high in antioxidants like anthocyanins and quercetin, which support heart health, lower blood sugar, and may help prevent cancer.

Red onions and yellow onions are nutritionally similar, but red onions generally contain higher levels of certain antioxidants, specifically anthocyanins, which give them their red color.

Red onions are a good source of fiber and prebiotics like fructans. These feed the beneficial bacteria in your gut, which can improve digestive health and boost immunity.