Onion: calories and nutrition facts
Calories in onion per 100 g and per typical portion, from the MacroLab food catalog.
40kcal per 100 g
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To burn these 40 calories:
- 9minWalking (5 km/h)
- 4minRunning (8 km/h)
- 5minCycling (16–19 km/h)
- 5minSwimming
Times use the MET equation for a 70 kg adult. Actual burn varies with your weight, age and pace.
Calories per portion
Common portions from the MacroLab catalog, next to the 100 g reference.
| Portion | kcal |
|---|---|
| 100 g | 40 |
| 1 piece (110 g) | 44 |
Can onion make you gain weight?
At 40 kcal per 100 g, this is a food with very low energy density: it takes about 250 g to reach 100 kcal.
One piece (110 g) has only 44 kcal, which is easy to fit into most days.
No single food makes you gain weight. What matters is your total calories over days and weeks compared with what you burn.
Onion vs other foods in “Vegetables”
It has 9% more calories than the average food in “Vegetables” (37 kcal per 100 g).
| Per 100 g | This food | Group average |
|---|---|---|
| Energy | 40 kcal | 37 kcal |
Related foods
Frequently asked questions
- How many calories are in 100 g of onion?
- 100 g has 40 kcal. That means about 250 g for every 100 kcal.
- How many calories are in one piece of onion?
- One piece (110 g) has 44 kcal.
Log onion with a photo in MacroLab
Snap your plate and MacroLab estimates calories and macros, then keeps your daily targets up to date.
Data from the MacroLab food catalog, updated September 26, 2026. Values vary by variety and brand; check the label of the product you buy.