Onions serving size, cups to grams
Here a serving of raw onions is counted as 1 medium raw onion, which USDA weighs at 3.9 oz (110 g), with 44 calories and 1.2 g protein. One cup weighs 5.6 oz (160 g).
Serving sizes of raw onions
Every household measure USDA weighs for this food, plus 1 oz and 100 g.
| Measure | Weight | Calories | Protein | Carbs | Fat |
|---|---|---|---|---|---|
| 1 cup, chopped | 5.6 oz (160 g) | 64 calories | 1.8 g | 14.9 g | 0.16 g |
| 1 cup, sliced | 4.1 oz (115 g) | 46 calories | 1.3 g | 10.7 g | 0.12 g |
| 1 tbsp chopped | 10 g | 4 calories | 0.11 g | 0.93 g | 0.01 g |
| 1 large | 5.3 oz (150 g) | 60 calories | 1.6 g | 14 g | 0.15 g |
| 1 medium | 3.9 oz (110 g) | 44 calories | 1.2 g | 10.3 g | 0.11 g |
| 1 small | 2.5 oz (70 g) | 28 calories | 0.77 g | 6.5 g | 0.07 g |
| 10 rings | 2.1 oz (60 g) | 24 calories | 0.66 g | 5.6 g | 0.06 g |
| 1 slice, large | 1.3 oz (38 g) | 15 calories | 0.42 g | 3.5 g | 0.04 g |
| 1 slice, medium | 14 g | 6 calories | 0.15 g | 1.3 g | 0.01 g |
| 1 slice, thin | 9 g | 4 calories | 0.1 g | 0.84 g | 0.01 g |
| 1 oz | 1 oz (28 g) | 11 calories | 0.31 g | 2.6 g | 0.03 g |
| 100 g | 3.5 oz (100 g) | 40 calories | 1.1 g | 9.3 g | 0.1 g |
Cups to grams
USDA weighs 1 cup (chopped) of raw onions at 160 g. Smaller cup measures follow from it.
| Measure | Weight | Calories |
|---|---|---|
| 1 cup | 5.6 oz (160 g) | 64 calories |
| 3/4 cup | 4.2 oz (120 g) | 48 calories |
| 2/3 cup | 3.8 oz (107 g) | 43 calories |
| 1/2 cup | 2.8 oz (80 g) | 32 calories |
| 1/3 cup | 1.9 oz (53 g) | 21 calories |
| 1/4 cup | 1.4 oz (40 g) | 16 calories |
Grams and ounces to cups
| Weight | Volume | Calories |
|---|---|---|
| 1 oz | 1/8 cup | 11 calories |
| 100 g (3.5 oz) | 2/3 cup | 40 calories |
| 1 lb (454 g) | 2 3/4 cups | 181 calories |
What 3.5 oz (100 g) of onions looks like
3.5 oz (100 g) of raw onions is 3.5 oz, or about 2/3 cup or 1 medium onion. It has 40 calories, 1.1 g protein, 9.3 g carbs and 0.1 g fat. One medium onion weighs 3.9 oz (110 g).
Raw, cooked and other forms
The same measure weighs differently once food is cooked, dried or canned, and so do the calories in it. USDA numbers for each form:
| Form | USDA measure | Calories per 3.5 oz (100 g) | Protein per 3.5 oz (100 g) |
|---|---|---|---|
| Raw onions | 1 cup (chopped): 5.6 oz (160 g) | 40 calories | 1.1 g |
| Boiled onions | 1 cup: 7.4 oz (210 g) | 44 calories | 1.4 g |
| Canned onions | 1/2 cup (chopped or diced): 4 oz (112 g) | 19 calories | 0.85 g |
Keep exploring
Sources
Weights and nutrition: USDA FoodData Central, food portions and nutrients (FoodData Central, April 2026 release, accessed 2026-10-14)
- Raw onions: Onions, raw, FDC ID 170000 (SR Legacy, published 2019-04-01) · full nutrition facts
- Boiled onions: Onions, cooked, boiled, drained, without salt, FDC ID 170001 (SR Legacy, published 2019-04-01)
- Canned onions: Onions, canned, solids and liquids, FDC ID 170003 (SR Legacy, published 2019-04-01)
- Kitchen measures (1 cup = 16 tbsp, 1 tbsp = 3 tsp): NDSU Extension, Ingredient Substitutions (FN198, J. Garden-Robinson, April 2013 edition). https://www.extension.purdue.edu/extmedia/HHS/HHS-784-W.pdf (accessed 2026-10-12)
How we calculate: each household measure is the gram weight USDA lists for this food. Calories and nutrients are the USDA values per 3.5 oz (100 g) scaled to that weight. 1 oz = 28.35 g and 1 lb = 453.6 g. Cup fractions are rounded to the nearest kitchen measure. A dash (—) means USDA reports no value. How we verify.