Onion Calories & Nutrition Facts
Contains quercetin and allicin with potent anti-inflammatory and antibacterial properties.
Quick answer
How many calories are in Onion?
Onion has 40 calories per 100g. A 1 cup, chopped (160g) has about 64 calories. It is a low-calorie food, with most calories coming from carbs.
Start with your portion
Turn Onion into a daily plan
Practical Portion Guide for Onion
| Portion | Calories | Protein | Carbs | Net carbs | Fat |
|---|---|---|---|---|---|
| 1 cup, chopped (160g) | 64 kcal | 1.8g | 14.9g | 12.2g | 0.2g |
| 1 cup, sliced (115g) | 46 kcal | 1.3g | 10.7g | 8.7g | 0.1g |
| 1 tbsp chopped (10g) | 4 kcal | 0.1g | 0.9g | 0.8g | 0.0g |
| 100g USDA reference | 40 kcal | 1.1g | 9.3g | 7.6g | 0.1g |
Use gram-based portions when precision matters, especially during weight loss or macro tracking.
% Daily Value: 1 cup, chopped (160g) vs 100g
Percent Daily Values use the FDA reference amounts for adults (protein 50g, fiber 28g, carbohydrate 275g, fat 78g, sodium 2,300mg, cholesterol 300mg, potassium 4,700mg). The FDA label guide treats 20% DV or more per serving as high and 5% DV or less as low. Potassium comes from USDA FoodData Central FDC ID 170000 (Onions, raw); the other values are this page's 100g reference scaled to the portion.
| Nutrient | Per 100g | % DV | 1 cup, chopped (160g) | % DV |
|---|---|---|---|---|
| Protein | 1.1g | 2% | 1.8g | 4% |
| Dietary fiber | 1.7g | 6% | 2.7g | 10% |
| Total carbohydrate | 9.3g | 3% | 14.9g | 5% |
| Total fat | 0.1g | 0% | 0.2g | 0% |
| Sodium | 4mg | 0% | 6mg | 0% |
| Cholesterol | 0mg | 0% | 0mg | 0% |
| Potassium (USDA) | 146mg | 3% | 234mg | 5% |
Source: FDA Daily Values (21 CFR 101.9), checked September 17, 2026. USDA record: FDC ID 170000.
Serving Size Calculator
Macros Breakdown (per 100g)
Diet Suitability
Glycemic Index: 15 (Low)
How Onion Fits Into a Diet
Onion can fit a balanced diet when portioned against your calorie and macro targets.
Build meals around protein, fiber, and minimally processed ingredients to make the portion more filling.
Preparation method, brand, and added ingredients can change the final nutrition values.
Plan Around Onion
Zero-Calorie Foods Guide
Use low-calorie vegetables like Onion to increase meal volume.
Calorie Deficit Calculator
Estimate the daily calorie target that turns low-calorie foods into a real plan.
Keto Diet Guide
Check how low-carb foods like Onion fit within a ketogenic day.
Calorie Calculator
Calculate your daily intake target before choosing serving sizes.
Compare Onion With Similar Vegetables
Use this comparison when choosing a serving. Calories alone do not tell the full story: protein, fiber, fat, sodium, and realistic portion size determine whether a food fits your plan.
| Food | Calories | Protein | Carbs | Fat | Fiber |
|---|---|---|---|---|---|
| Onion | 40 kcal | 1.1g | 9.3g | 0.1g | 1.7g |
| Broccoli | 34 kcal | 2.8g | 7g | 0.4g | 2.6g |
| Spinach | 23 kcal | 2.9g | 3.6g | 0.4g | 2.2g |
| Carrot | 41 kcal | 0.9g | 10g | 0.2g | 2.8g |
| Tomato | 18 kcal | 0.9g | 3.9g | 0.2g | 1.2g |
| Cucumber | 15 kcal | 0.7g | 3.6g | 0.1g | 0.5g |
All comparison values use each food's 100-unit reference so foods can be compared on the same basis.
Vitamins & Minerals
Vitamins
Minerals
Complete Nutrition Facts (per 100g)
% DV = percent of the FDA Daily Value for a 2,000-calorie diet, per 100g. Total sugars have no Daily Value; the FDA value applies to added sugars only.
Methodology & Nutrition Data Sources
How we calculate nutrition data for Onion: Calorie and macronutrient values are standardized reference profiles, generally based on USDA FoodData Central entries where available, then scaled to the serving you choose. Entries may come from different FDC data types or releases, and brand or preparation differences can change the numbers.
- Calorie and macronutrient data sourced from the USDA FoodData Central , the federal food composition database used as the main reference where a matching entry exists.
- Daily Value context: for % DV comparisons, use the FDA Daily Value reference amounts for a 2,000 calorie diet (21 CFR 101.9).
- Dietary reference intakes (DRI) for vitamins and minerals are available in the National Academies Dietary Reference Intake tables for further reading; this page does not calculate DRI percentages.
- Glycemic index values are approximate listed values; GI varies by variety, ripeness, and preparation, so compare with the Harvard Health Glycemic Index Reference and the University of Sydney GI database.
- Dietary guidelines context from the HHS/USDA Dietary Guidelines for Americans 2020–2025 , the federal evidence-based nutrition guidance.
Authoritative nutrition data sources:
- USDA FoodData Central, comprehensive food composition database
- FDA Nutrition Facts Label rules, % Daily Value methodology
- NIH Office of Dietary Supplements, vitamin and mineral research
- CDC Nutrition, Public Health Guidance, chronic disease and diet
- HHS/USDA Dietary Guidelines 2020–2025, federal nutrition recommendations
- Harvard T.H. Chan School of Public Health, The Nutrition Source, evidence-based dietary guidance
Nutrition Disclaimer: Calorie and nutrient values are generally based on USDA reference data and may vary by brand, preparation method, ripeness, and cooking technique. These values are for informational purposes only and should not replace personalized dietary advice from a registered dietitian. Individuals with medical conditions should consult a healthcare provider before making significant dietary changes.
Reviewed by Priya Lindqvist · Last updated September 17, 2026 · Values may not reflect the newest USDA FoodData Central release
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Frequently Asked Questions
How many calories are in 1 cup, chopped Onion?
1 cup, chopped (160g) of Onion has about 64 calories, 1.8g protein, 14.9g carbohydrates, 2.7g fiber, and 0.2g fat. The 160g portion weight is the USDA FoodData Central household measure for FDC ID 170000 (Onions, raw), scaled from the 100g reference values.
Is Onion high in protein?
Onion has 1.1g protein per 100g, which is 2% of the 50g FDA Daily Value. 1 cup, chopped (160g) supplies about 1.8g, or 4% DV. Under the FDA label guide (20% DV or more per serving is high, 5% or less is low), that serving counts as a low-protein serving.
Is Onion a good source of potassium?
USDA FoodData Central lists 146mg potassium per 100g for Onions, raw (FDC ID 170000), which is 3% of the 4,700mg Daily Value. 1 cup, chopped (160g) provides about 234mg, or 5% DV, a low contribution by the FDA 5% guide.
How many calories are in Onion?
Onion contains 40 calories per 100g serving. Using general 4-4-9 calorie factors, that is roughly 4 calories from protein, 37 calories from carbohydrates, and 1 calories from fat; these estimates may not add up exactly to the listed total.
Is Onion good for weight loss?
Yes, Onion is excellent for weight loss with only 40 calories per 100g. It is low in calories and can help you feel satisfied while maintaining a calorie deficit.
How much protein is in Onion?
Onion contains 1.1g of protein per 100g. This is a relatively low protein food; consider pairing it with higher protein sources.
What serving size should I track for Onion?
Track Onion by grams when precision matters. A practical starting point is 1 cup, chopped (160g), which is about 64 calories. For packaged, restaurant, fried, sauced, or sweetened versions, use the product label because brand formulas can differ from the plain reference.
Is Onion keto-friendly?
Yes, Onion is keto-friendly with only 9.3g of carbohydrates per 100g. It fits well within the typical keto macro limits of 20-50g net carbs per day.
Is Onion good for diabetics?
Onion may fit a diabetes meal plan with a listed glycemic index of 15, but the useful decision is the actual portion, total carbohydrates, added sugar, and the rest of the meal. People using diabetes medication should follow personalized clinical guidance.
What vitamins and minerals are in Onion?
Calorique's food profile lists vitamins C, B6, Folate, B1 and minerals including Potassium, Manganese, Copper for Onion. These are general highlights, not measured amounts or a "good source" rating; check USDA FoodData Central or the product label for exact micronutrient values.
Where does Calorique get nutrition data for Onion?
Calorique standardizes Onion nutrition values per 100g using USDA FoodData Central reference fields where available, then scales the data into realistic serving sizes. FDA Nutrition Facts methodology and authoritative nutrition references are used for context. This page was last reviewed September 17, 2026.
Related Calculators
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Cucumber
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Sweet Potato
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