Calories in an Onion: Small, Medium, Large and Cooked

Onions are in almost every kitchen. They go into soups, sauces, salads, burgers, stir-fries and stews, and they add a lot of flavor. If you count calories, you might wonder whether you need to count onions at all.

The short answer: a medium onion (110 g) has about 44 calories, a small one about 28 and a large one about 60. 100 g of raw onion has about 40 calories. Onions are very low in calories and give you some fiber and vitamin C. The calories come from oil, butter, batter and frying.

Calories in an onion by size

Values are for raw onions, from the US Department of Agriculture (USDA FoodData Central):

Onion	Weight	Calories
1 tbsp chopped	10 g	4 kcal
1 slice (⅛” thick)	14 g	6 kcal
Small	70 g	28 kcal
100 g	100 g	40 kcal
Medium (2½” across)	110 g	44 kcal
Large	150 g	60 kcal
1 cup chopped	160 g	64 kcal
1 cup boiled onion	210 g	92 kcal

Tip: a few slices of onion on a burger or salad add fewer than 10 calories. You don’t need to worry about them – but you do need to count the oil they’re cooked in.

Onion nutrition facts

Nutrient	Per 100 g	Per medium onion (110 g)
Calories	40 kcal	44 kcal
Carbohydrates	9.3 g	10.3 g
– of which sugars	4.2 g	4.7 g
Fiber	1.7 g	1.9 g
Protein	1.1 g	1.2 g
Fat	0.1 g	0.1 g
Vitamin C	7.4 mg	8.1 mg
Folate	19 µg	21 µg
Potassium	146 mg	161 mg

Onions are mostly water and carbs, with almost no fat. They contain quercetin, a plant compound that colors the outer layers – red onions have the most. Onions are also rich in fructans, a type of fiber that feeds good gut bacteria. In some people, fructans cause gas and bloating. This is common with irritable bowel syndrome (IBS).

Red, sweet and green onions

Onion type (per 100 g)	Calories
Yellow, white or red onion	about 40 kcal
Sweet onion (like Vidalia)	32 kcal
Green onion (scallion)	32 kcal
Shallot	72 kcal
Boiled onion	44 kcal

The differences are small. Shallots are a bit higher because they have less water, but you use them in small amounts.

Calories in onion dishes

Dish	Portion	Calories
Sautéed onion with 1 tsp oil	1 medium onion	about 85 kcal
Caramelized onions with 1 tbsp oil or butter	1 large onion	about 160⁠–⁠180 kcal
Crispy fried onions (topping)	2 tbsp	about 40⁠–⁠45 kcal
Onion rings, breaded and fried	100 g	411 kcal
Onion rings, fast food order	about 18 rings (117 g)	481 kcal
French onion soup with bread and cheese	1 bowl	about 300⁠–⁠450 kcal
Onion dip (sour cream based)	2 tbsp	about 50⁠–⁠60 kcal
Whole fried “blooming” onion appetizer	1 onion	over 1,500 kcal

The onion is never the problem. Batter and deep-frying turn a 44-calorie onion into a 480-calorie side dish. Onion rings also have a lot of salt: an order has about 900 mg of sodium. French onion soup gets most of its calories from the bread and melted cheese on top.

Are onions good for weight loss?

Yes. Onions add a lot of flavor for very few calories, so they make healthy meals taste better without extra fat or sugar.

How to use them:

• Cook them with a little oil – 1 teaspoon is enough for a pan of onions, especially with a lid or a splash of water.
• Add raw onion to salads, sandwiches and salsa for crunch.
• Use onions to replace part of the meat in sauces, chili and stews.
• Skip onion rings and blooming onions or share them.

Remember that you lose weight only when you eat fewer calories than you burn. Read more about the calorie deficit and find your number with our calorie calculator.

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You can also read how many calories are in a tomato and in a potato.

The bottom line

A medium onion has about 44 calories, a large one about 60 and 100 g about 40. Onions are low in calories, add a lot of flavor and give you some fiber and vitamin C. They’re great for weight loss – just watch the oil you cook them in, and keep onion rings and fried onion appetizers for rare treats.