How many calories are in an onion?

A medium onion of about 110 g has around 44 kcal.

Do I need to count onions?

Raw or boiled onions are so low in calories that small amounts make little difference. Count the oil you cook them in.

Calories in an onion

A medium onion has about 44 kcal. When you fry onions, the oil adds far more calories than the onion itself.

By the Calori team · Updated 21 October 2026 · 3 min read

Onion calories by portion

Portion	Calories	Protein	Carbs	Fat
Small onion (70 g)	28 kcal	0.8 g	5.3 g	0.1 g
Medium onion (110 g)	44 kcal	1.2 g	8.4 g	0.1 g
Large onion (150 g)	60 kcal	1.7 g	11.4 g	0.2 g
Medium onion fried in 1 tbsp oil	160 kcal

Onion nutrition per 100 g

Energy	40 kcal (167 kJ)
Protein	1.1 g
Carbohydrate	7.6 g
of which sugars	4.2 g
Fat	0.1 g
Fibre	1.7 g

Typical values. Carbohydrate excludes fibre, as on UK food labels. Brands and varieties differ, so check the label where there is one.

Fried onions

Onions soak up oil as they soften. Frying a medium onion in a tablespoon of oil takes it from about 44 kcal to around 160. Using a spray oil or a splash of water to soften them keeps that down.

Log it without looking it up

Calori recognises foods like this from a photo and estimates the portion, so you can log a whole plate in one go. Set your daily target with our calorie calculator.

More calorie counts

Banana, Egg, Chicken breast, Avocado, Apple, Sweet potato, Potato, Rice, Porridge oats, Strawberries, Kiwi, Orange, Carrot, Cucumber, Broccoli, Salmon, Greek yoghurt, Milk, Bread, Pasta, Peanut butter, Almonds, Sugar, Guinness, Greggs sausage roll, Blueberries, Grapes, Pear, Tomato, Mango, Pineapple, Watermelon, Chicken thigh, Beef mince, Cod, Tinned tuna, Prawns, Cottage cheese, Cheddar, Butter, Olive oil, Hummus, Crumpet, Bagel, Tortilla wrap, Baked beans, Mushrooms, Spinach, Peas, Lentils, Chickpeas, Tofu, Dark chocolate, Crisps, Popcorn, or see all calorie counts.

Frequently asked questions

How many calories are in an onion?: A medium onion of about 110 g has around 44 kcal.
Do I need to count onions?: Raw or boiled onions are so low in calories that small amounts make little difference. Count the oil you cook them in.