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Calories in an onion

A usual serving, 1 onion (110 g), has about 45 kcal; 100 g ≈ 40 kcal.

Serving kcal Protein Fat Carbs Fibre
100 g 40 1.1 g 0.1 g 7.6 g 1.7 g
1 onion 110 g 44 1.2 g 0.1 g 8.4 g 1.9 g

Source: fdc.nal.usda.gov · Confidence: high · Updated:

Calories per serving

Serving kcal Protein Fat Carbs
1 onion 110 g 44 1.2 g 0.1 g 8.4 g
Half an onion 55 g 22 0.6 g 0.1 g 4.2 g

How it fits into a day

An onion of about 110 g has about 45 kcal. Onion itself is light; the calories in a dish come from the oil it's fried in, because onion soaks it up easily. Most of the energy, about 85%, comes from carbs.

A usual serving (1 onion) is about 2% of a 2,000 kcal day. How much do you need a day? Work it out in the calorie calculator.

Lighter options

  • A tablespoon of oil is enough to sweat onions; if you need more, add a splash of water.
  • Raw onion with beans or cevapi barely changes your daily total.

Frequently asked questions

How many calories are in an onion?

About 45 kcal in 110 g, with 1.2 g protein, 0.1 g fat and 8.4 g carbs.

How many calories are in 100 g of onion?

About 40 kcal per 100 g: 1.1 g protein, 0.1 g fat and 7.6 g carbs, plus 1.7 g fibre.

Does fried onion have more calories?

The onion itself gains no calories, but it soaks up some of the oil from the pan. So count onion and oil separately: onion is about 40 kcal per 100 g, and oil goes by the spoonful.

See also

Full table: Vegetables, salads and spreads