Cooked onion calories come to 92 for one cup (210 g) and 44 per 100 g, based on onions boiled, drained and cooked without salt. Most of that energy is carbohydrate, and the sodium is close to zero. In the pan, the onion itself is rarely what drives the total. Whatever you cook it in usually is.
92kcal
1 cup · 210 g, boiled, drained, unsalted
11%protein
2.9 gProtein
21 gCarbs
0.4 gFat
How to burn off 92 kcal
—Walking, brisk
—Jogging
—Cycling, moderate
—Swimming
Skip the math. BodyPal counts these calories from your steps and workouts automatically.
Nutrition facts
Boiled, drained, unsalted · per 210 g
Calories
92 kcal
Protein
2.9 g
Carbohydrate
21 g
Fat
0.4 g
Saturated fat
0.1 g
Cholesterol
0 mg
Sodium
6 mg
Potassium
349 mg
Iron
0.5 mg
Source: USDA FoodData Central
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Verified nutrition data
Numbers on this page come from USDA FoodData Central, the U.S. Department of Agriculture’s food composition database, and from manufacturer labels where a branded product is named. Last verified September 2026. How we verify our data →
Cooked onion: calories, protein and sodium by serving
Percent of daily value uses the FDA reference of 2,000 kcal a day.
Serving
kcal
Protein
Carbs
Fat
Sodium
% DV kcal
1 cup (210 g)
92
2.9 g
21.3 g
0.4 g
6 mg
5%
1 medium (94 g)
41
1.3 g
9.5 g
0.2 g
3 mg
2%
1 large (128 g)
56
1.7 g
13 g
0.2 g
4 mg
3%
100 g
44
1.4 g
10.2 g
0.2 g
3 mg
2%
3 × 1 cup (210 g)
277
8.6 g
19 mg
5 × 1 cup (210 g)
462
14.3 g
32 mg
A cup of cooked onion is a 92-calorie side
A full cup of boiled onion, 210 g, lands at 92 calories, about 5 percent of a 2,000-calorie daily value. A medium onion (94 g) cooked down comes to 41 calories, and a large one (128 g) to 56. Those are small numbers for a vegetable that fills a lot of space on a plate.
Onions shrink as they cook, so a cup of cooked onion takes more raw onion than you might expect. That matters when you log. If you sliced a whole medium onion into a stir-fry, count the medium onion. If you scooped a cup from a pot of smothered onions, count the cup.
Big batches stay modest too. Two cups (420 g) come to 185 calories, three cups (630 g) to 277, and five cups (1,050 g), the kind of volume you might caramelize for a week of meals, add up to 462. Even that pile carries just 32 mg of sodium. Onions on their own almost never break a calorie budget.
Carbs supply 85 percent of the calories
The calorie split is lopsided: 85 percent from carbohydrate, 11 percent from protein and just 4 percent from fat. Per 100 g that works out to 10.2 g of carbs, 1.4 g of protein and 0.2 g of fat. Saturated fat and cholesterol both read 0.
Nearly half of those carbs are sugar, 4.7 g per 100 g and 9.9 g in a full cup. That natural sugar is why slow-cooked onions taste sweet and brown so well. It is also why a cup of cooked onion has more carbohydrate, 21.3 g, than many people assume for a savory vegetable.
Protein is not the reason to eat onions. A cup gives 2.9 g, about 6 percent of the daily value. Treat cooked onion as a flavor base and a source of bulk, and get your protein from whatever it is served with.
Unsalted onions carry almost no sodium
These numbers are for onions boiled without salt, and the sodium row shows it: 3 mg per 100 g and 6 mg per cup, which rounds to 0 percent of the 2,300 mg daily value. On a low-sodium plan, plain cooked onion is about as safe a choice as a vegetable gets.
The catch is everything around it. Salt in the cooking water, a splash of soy sauce, broth or a seasoning packet can add far more sodium than the onion ever will. If you watch sodium, season at the table, where you can see how much goes in, rather than in the pot.
Potassium is the quieter story. Cooked onion has 166 mg per 100 g against a 4,700 mg daily value, so it helps a little without being a major source. Fiber is similar: 2.9 g in a cup, measured against a daily value of 28 g, a useful contribution from a side you were adding for flavor anyway.
The cooking fat matters more than the onion
The data here describes boiled onion with 0.2 g of fat per 100 g. Sautéed, fried or caramelized onions start from the same vegetable but pick up whatever butter or oil goes into the pan. If your onions glisten, log the fat separately so the total reflects what you actually ate.
Because cooked onion is low in calories and high in volume, it works well for stretching a meal. Folding a cup into scrambled eggs, a bean chili or a lean ground-meat sauce adds sweetness and bulk for 92 calories. Pair it with a clear protein source, since the onion contributes little there.
Onions also show up hidden in soups, sauces and casseroles, where they are easy to forget when tracking. A quick way to catch them is to snap a photo of the plate; BodyPal can log the food from a photo, and you can adjust the onion portion afterward.
How does cooked onion compare?
Here is how cooked onion stacks up against red onion, cooked carrots and cooked broccoli, per 100 g and per usual serving.
Verdict: If you want the fewest calories per bite, pick cooked carrots or cooked broccoli at 35 per 100 g, and choose broccoli if protein matters, with 2.4 g per 100 g against 1.4 g for cooked onion. Cooked onion matches red onion at 44 per 100 g, and with just 3 mg of sodium it beats both carrots (58 mg) and broccoli (41 mg) on salt.
Cooked onion FAQs
How many calories are in cooked onions?
One cup of boiled, drained onion is 92 calories. A medium onion cooked the same way is 41 calories, and a large one is 56.
Are cooked onions good for weight loss?
A cup has 92 calories, 0.4 g of fat and 21.3 g of carbs, with 1.4 g of fiber per 100 g, so it fills a plate for few calories.
Cooked onion vs red onion: which has more calories?
Both land at 44 calories per 100 g, so boiling and draining without added fat leaves the count unchanged.
How many carbs and how much sugar are in cooked onions?
Per 100 g there are 10.2 g of carbs, of which 4.7 g are sugars. A full cup has 21.3 g of carbs and 9.9 g of sugars.
How many calories are in a medium cooked onion?
A medium cooked onion (94 g) has 41 calories. It also brings 9.5 g of carbs, 4.4 g of sugar, 1.3 g of fiber and 1.3 g of protein, with only 0.2 g of fat when boiled without salt.
How many calories are in a large cooked onion?
A large cooked onion (128 g) has 56 calories, about 3 percent of a 2,000-calorie daily value. That includes 13 g of carbs, 6.1 g of sugar and 1.8 g of fiber, plus just 4 mg of sodium.
How much fiber is in a cup of cooked onions?
A cup of cooked onions (210 g) has 2.9 g of fiber, measured against a 28 g daily value. Per 100 g the figure is 1.4 g, so a full cup is a modest but useful contribution.
Do boiled onions have much sodium?
No. Boiled onions cooked without salt have 3 mg of sodium per 100 g and 6 mg per cup, which rounds to 0 percent of the daily value. Salted water or sauces will raise that quickly.
How much protein is in cooked onions?
A cup of cooked onions has 2.9 g of protein, about 6 percent of the daily value. Protein supplies only 11 percent of the calories, while carbohydrate supplies 85 percent.
