VEGETABLE · per 100g edible portion
Onion
Nutrition facts for onion (raw) — measured values from USDA FoodData Central, standardized to a 100g basis.
Ranks in 8 of 8 tracked rankings
Energy
40kcal
per 100g
Per 1 slice, medium (1/8" thick) (14 g): 6 kcal · 0.2 g protein · 1.3 g carbs · 0 g fat
Protein
1.1g
Carbs
9.3g
Fiber
1.7g
Fat
0.1g
Macronutrient mix
Share of calories from each macro (Atwater 4/4/9 kcal per g)
Serving sizes
Household measures
| Measure | Grams | Calories | Protein | Carbs | Fat |
|---|---|---|---|---|---|
| 1 slice, medium (1/8" thick) | 14 g | 6 kcal | 0.2 g | 1.3 g | 0 g |
| 1 small | 70 g | 28 kcal | 0.8 g | 6.5 g | 0.1 g |
| 1 medium (2-1/2" dia) | 110 g | 44 kcal | 1.2 g | 10.3 g | 0.1 g |
| 1 large | 150 g | 60 kcal | 1.7 g | 14 g | 0.2 g |
Measures from USDA food portion data; per-serving values are derived from the measured per-100g values.
Full profile
Nutrition facts per 100g
| Nutrient | Amount |
|---|---|
| Calories | 40 kcal |
| Protein | 1.1 g |
| Carbohydrates | 9.34 g |
| Fiber | 1.7 g |
| Sugar | 4.24 g |
| Fat | 0.1 g |
| Saturated Fat | 0.04 g |
| Calcium | 23 mg |
| Iron | 0.21 mg |
| Magnesium | 10 mg |
| Phosphorus | 29 mg |
| Potassium | 146 mg |
| Sodium | 4 mg |
| Zinc | 0.17 mg |
| Vitamin A | 0 µg |
| Vitamin C | 7.4 mg |
| Vitamin D | 0 µg |
| Vitamin E | 0.02 mg |
| Vitamin K | 0.4 µg |
| Vitamin B1 | 0.05 mg |
| Vitamin B2 | 0.03 mg |
| Vitamin B3 | 0.12 mg |
| Vitamin B6 | 0.12 mg |
| Vitamin B12 | 0 µg |
| Folate | 19 µg |
Common questions
Onion FAQ
How many calories in 1 slice, medium (1/8" thick) of onion?
1 slice, medium (1/8" thick) of onion (14 g) provides about 6 kcal. Per 100 g, onion has 40 kcal.
How much protein in onion?
Onion contains 1.1 g of protein per 100 g — about 0.2 g per 1 slice, medium (1/8" thick) (14 g).
Is onion high in fiber?
Onion has 1.7 g of fiber per 100 g and ranks #37 of 58 tracked foods for fiber.
Explore
Where onion ranks
Food graph
Nutritionally similar to onion
Computed from all 25 tracked nutrient profiles in the database — closest overall composition, not necessarily the same food family.
Keep exploring
Related vegetables
Data Provenance
USDA FoodData Central
SR Legacy
- Source
- USDA FoodData Central
- FDC ID
- 170000
- Basis
- 100 g edible portion
- Record type
- SR Legacy
- Retrieved
- November 10, 2026