Onion Nutrition Facts
A 100 g serving of onion contains 40 kcal, 1.1g protein (lime), 0.1g fat (pink) and 9g carbohydrate (blue). It has modest fiber and 4.2g sugar. Its other nutrient values are modest — see the full breakdown below.
Core Nutrients per 100 g
PER 100 G SERVINGThe six values MacroDrop shows on every meal card: energy, the three macros, fiber and sugars.
Extended Nutrients
PER 100 G SERVINGGrouped as in the app: lipids, minerals, vitamins and other compounds sit one level below the core six. Daily values follow the FDA 2,000 kcal reference.
How Cooking Changes The Numbers
Per 100 g, from each preparation's own USDA data.
| Preparation | Kcal | Protein | Fat | Carbs | Note |
|---|---|---|---|---|---|
| Raw | 40 | 1.1 g | 0.1 g | 9 g | Reference entry |
| With salt | 42 | 1.4 g | 0.2 g | 9 g | Cooked, boiled, drained, with salt |
| Without salt | 44 | 1.4 g | 0.2 g | 10 g | Cooked, boiled, drained, without salt |
Understanding Onion Nutrition
Onion is a low-calorie vegetable that delivers fiber, vitamins and minerals for very few calories. At 40 kcal per 100 g serving, it provides 1.1g of protein, 9g of carbohydrate and 0.1g of fat. Onion is particularly rich in vitamin C, delivering 8mg — 8% of the daily value — in a single serving. It has modest fiber and 4.2g sugar.
For athletes and anyone tracking macros, onion is a straightforward source of carbohydrate energy, useful around training for topping up glycogen. Its fiber and micronutrient content makes it a useful addition to a balanced macro split without pulling calories too high.
Frequently Asked Questions
How many calories are in a 100 g serving of onion?
A 100 g serving of onion has 40 kcal, 1.1g protein, 0.1g fat and 9g carbohydrate.
How much protein is in onion?
1.1g per 100 g serving.
Is onion high in sugar or fiber?
It has modest fiber and 4.2g sugar — 1.7g fiber and 4.2g sugar per 100 g serving.
Which nutrients is onion richest in?
No single micronutrient stands out sharply — see the full breakdown below.
Is onion good for tracking macros?
For athletes and anyone tracking macros, onion is a straightforward source of carbohydrate energy, useful around training for topping up glycogen.
Does cooking onion change its nutrients?
Cooked onion runs about the same in calories per equivalent serving compared to the raw reference — see the cooking table above for specific preparations.
Log the onion in two seconds
MacroDrop tracks all of these nutrients — core and extended — from a photo, your voice or a barcode. Offline USDA database, 7,800 foods.
Values come from the USDA FoodData Central entry Onions, raw (FDC ID 170000), per 100 g. Daily values follow the FDA 2,000 kcal reference. Last reviewed August 2026.