Calories in Onions
40 calories per 100g (100g)
Raw onions are a low-calorie vegetable, providing just 40 calories per 100 grams. A single medium onion (about 110g) contains roughly 44 calories, making it an excellent way to add bold flavor to meals without significantly impacting your daily calorie budget. Most of those calories come from carbohydrates, with virtually no fat.
Calories by Portion Size
| Portion | Weight | Calories |
|---|---|---|
| 1 slice (thin, ~14g) | 14g | 6 |
| 1 tablespoon chopped (~10g) | 10g | 4 |
| ¼ cup chopped (~40g) | 40g | 16 |
| ½ cup chopped (~80g) | 80g | 32 |
| 1 cup chopped (~160g) | 160g | 64 |
| 1 small onion (~70g) | 70g | 28 |
| 1 medium onion (~110g) | 110g | 44 |
| 1 large onion (~150g) | 150g | 60 |
Protein
1.1g
11% of calories
Carbs
9.34g
93% of calories
Fat
0.1g
2% of calories
How does this compare?
Raw onions are among the lowest-calorie options in the vegetables category — comparable to celery and cucumber — and significantly lighter than starchy vegetables like corn (86 cal/100g) or peas (81 cal/100g). They deliver a strong flavor punch per calorie, making them one of the most calorie-efficient aromatics you can add to a dish.
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- 1.
Use raw onions as a topping instead of higher-calorie condiments like mayo or cheese — a generous handful adds flavor for under 20 calories.
- 2.
Chopping onions finely lets you spread flavor throughout a dish using a smaller amount, keeping portions — and calories — naturally low.
- 3.
Raw onions have fewer calories than caramelized or sautéed onions cooked in oil or butter, so opt for raw when calorie counts matter.
- 4.
One cup of chopped raw onion is only 64 calories and provides 1.7g of fiber per 100g, helping you feel fuller when added to salads, salsas, or grain bowls.
- 5.
Pre-chop a batch of raw onions to keep in the fridge — having them ready makes it easy to add a low-calorie flavor boost to any meal without reaching for higher-calorie seasonings.
Common Questions About Calories in Onions
How many calories are in a whole raw onion?
A small onion (70g) has about 28 calories, a medium onion (110g) has about 44 calories, and a large onion (150g) has about 60 calories, based on USDA data of 40 calories per 100g.
Are raw onions good for weight loss?
Raw onions are very low in calories (40 per 100g) and contain fiber, which can support satiety. They're a practical way to add volume and flavor to meals without adding significant calories — but no single food causes or prevents weight loss on its own.
How many carbs are in raw onions?
Raw onions contain 9.34g of carbohydrates per 100g, of which 4.24g are natural sugars and 1.7g is dietary fiber. A medium onion (110g) has roughly 10.3g of total carbs.
Do raw onions have more calories than cooked onions?
Raw onions have 40 calories per 100g. Cooking methods matter: onions sautéed or caramelized in oil or butter will have more calories due to the added fat, while plain boiled onions are similar in calorie count to raw.