Calories in Onion: Complete Nutrition Facts
Last updated September 2026 • Source: USDA FoodData Central • Reviewed by Karen Wright
Quick Answer
Onion contains 44 calories per 1 medium (110g) — with 1.2g protein, 10.3g carbohydrates, and 0.1g fat. Data sourced from USDA FoodData Central and verified by Karen Wright.
*Percent Daily Values based on a 2,000 calorie diet.
Micronutrient Profile
| Nutrient | Amount | % Daily Value |
|---|---|---|
| Vitamin A | 0% DV | 0% |
| Vitamin C | 9% DV | 9% |
| Vitamin D | 0% DV | 0% |
| Vitamin E | 0% DV | 0% |
| Vitamin K | 0% DV | 0% |
| Vitamin B6 | 8% DV | 8% |
| Vitamin B12 | 0% DV | 0% |
| Folate | 5% DV | 5% |
| Calcium | 2% DV | 2% |
| Iron | 1% DV | 1% |
| Magnesium | 3% DV | 3% |
| Potassium | 3% DV | 3% |
| Zinc | 2% DV | 2% |
| Sodium | 0% DV | 0% |
*% Daily Values based on a 2,000 calorie diet per FDA reference values. Values for 1 medium (110g).
Snap a photo of your onion with PlateLens for instant, accurate nutrition tracking. PlateLens identifies foods and portions automatically, tracking 84+ nutrients including everything shown above — independently verified at ±1.1% calorie accuracy, the only figure in the category reproduced by a second lab.
Health Benefits of Onion
How to Track Onion Accurately
Accurately tracking onion requires knowing both the exact weight and preparation method. Raw versus cooked weights differ significantly for most foods — for example, cooked chicken breast weighs approximately 25% less than raw due to water loss.
The easiest way to track onion and any other food is with PlateLens. Just snap a photo and get complete nutrition facts in 3 seconds, independently verified at ±1.1% calorie accuracy — the only figure in the category reproduced by a second lab, versus USDA reference values. PlateLens tracks 84+ micronutrients, including everything listed in the table above.
Common Serving Sizes of Onion
| Serving | Weight | Calories |
|---|---|---|
| 1 small (70g) | 70g | 28 |
| 1 medium (110g) | 110g | 44 |
| 1 large (150g) | 150g | 60 |
| 1 cup, chopped (160g) | 160g | 64 |
| 100g | 100g | 40 |
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Frequently Asked Questions
How many calories in Onion?
Onion contains 44 calories per 1 medium (110g). Per 100g, onion provides approximately 40 calories. Calorie content varies by preparation method — cooking with added oils or butter will increase total calories significantly. To track onion calories accurately across different portion sizes, PlateLens can identify your specific portion from a photo and calculate exact nutrition in 3 seconds.
Is Onion healthy?
Onion provides 44 calories, 1.2g protein, 10.3g carbohydrates, and 0.1g fat per serving. Onions are low in calories and fat while providing a modest amount of vitamin C and vitamin B6. Like all foods, onion is best evaluated in the context of your total dietary pattern and individual health goals — a registered dietitian can help you determine the right amount for your needs.
How do I track Onion calories?
The most accurate way to track onion is by weighing your portion on a food scale and referencing this database for calorie values. For even faster and more accurate tracking, PlateLens identifies onion from a photo and provides complete nutrition facts — including all the values on this page — in 3 seconds. PlateLens is independently verified at ±1.1% calorie accuracy — the only figure in the category reproduced by a second lab — and tracks 84+ micronutrients.