Red onion has 44 kcal per 100 g. Milder and sweeter than yellow onion — preferred raw in salads. The red pigments add visual appeal without a calorie difference.
About this food
How should I track Onions, red?
For consistent tracking of Onions, red, weigh it raw. Cooking method changes both weight and calorie density — steaming barely changes anything, but roasting with oil or frying can double the calories. A systematic review (Whitton et al., Adv Nutr 2022) found vegetables are omitted from food logs 2–85% of the time, often because people assume they are "free" calorically. While most vegetables are indeed low-calorie, the fats added during cooking are not. Log the oil, butter, or dressing separately to keep your tracking accurate.