Vegetables
Onion nutrition facts
A 1 undetermined cup, chopped (160 g) serving of onion provides 64 calories, 2 g protein, 15 g carbohydrate, and 0 g fat — about 10% of its calories from protein, 88% from carbohydrate, and 2% from fat. The interactive label below toggles between a serving and 100 g.
Calorie split
Vitamins & minerals
Per serving (160 g)
- Vitamin C
- 11.8 mg
- Vitamin E
- 0.03 mg
- Vitamin K
- 0.64 mcg
- Thiamin (B1)
- 0.07 mg
- Riboflavin (B2)
- 0.04 mg
- Niacin (B3)
- 0.19 mg
- Vitamin B6
- 0.19 mg
- Folate (DFE)
- 30.4 mcg
- Magnesium
- 16.0 mg
- Phosphorus
- 46.4 mg
- Zinc
- 0.27 mg
- Copper
- 0.06 mg
- Manganese
- 0.21 mg
- Selenium
- 0.80 mcg
Nutrition highlights
Per 1 undetermined cup, chopped (160 g), onion is a good source of Vitamin C, Vitamin B6, and Dietary Fiber.
% of the FDA Daily Value per 1 undetermined cup, chopped (160 g) serving.
Key metrics
Nutrient density
Per 100 kcal, onion delivers about 7% of a Daily Value on average across 22 beneficial nutrients. The score is its percentile for that measure among the 177 foods in our database — higher means more nutrition per calorie. How this is calculated.
Density counts protein, fiber, and vitamins and minerals (not fat, sodium, or sugar), each capped so a single nutrient can’t dominate, with a calorie floor so very-low-calorie foods aren’t overstated. It measures nutrition per calorie within our database — a useful guide, not a complete verdict on how “healthy” a food is.
Similar foods & swaps
The closest vegetables to onion by nutrition (per 100 g), and how each differs.
Questions
- How many calories are in onion?
- A 1 undetermined cup, chopped (160 g) serving of onion has about 64 calories. Per 100 g, it has 40 calories — a low calorie density.
- How much protein is in onion?
- Onion provides about 2 g of protein per 1 undetermined cup, chopped (160 g) serving.
- What are the macros in onion?
- Per serving, onion has roughly 2 g protein, 15 g carbohydrate, and 0 g fat. By calories, that is 10% protein, 88% carbohydrate, and 2% fat.
- Is onion high in protein?
- Onion has a protein density of about 2.8 g per 100 kcal, and 10% of its calories come from protein. Foods above roughly 10 g per 100 kcal are generally considered protein-dense.
- What vitamins and minerals are in onion?
- Per 1 undetermined cup, chopped (160 g), onion is a notable source of Vitamin C and Vitamin B6. The label above lists the full micronutrient profile with % Daily Values.
Use it
More vegetables
References & methodology
- Data source: U.S. Department of Agriculture, Agricultural Research Service — FoodData Central, FDC ID 170000 (public domain).
- Daily Values: FDA Nutrition Facts label, 2016 update (adults and children aged 4+).
- Source claims: a serving supplying 10–19% of the Daily Value is a “good source”; 20% or more is an “excellent source” (FDA, 21 CFR 101.54).
- Calorie split: Atwater general factors — 4 kcal/g for protein and carbohydrate, 9 kcal/g for fat.
- Last reviewed: June 2026. Values are typical figures and vary with variety, ripeness, and preparation.
NutriFactsHub. “Onion Nutrition Facts.” https://www.nutrifactshub.com/foods/onion