48 %
Potassium contributes to normal functioning of the nervous system and to normal muscle function.
How many calories are in onions?
247kcal
in an 80 g portion
309 kcal per 100 g.
Source: UK CoFID 2021, record 13-590. Checked 5 October 2026.
0.96 gFat
7 gProtein
15.4 gFibre
48 %Daily potassium
What’s in an 80 g portion
More than half of a portion is carbohydrate. Sugars make up 43.5 g of that.
- 0.96 gFat
- 7 gProtein
- 56.2 gCarbohydrate
- 15.4 gFibre
- 3.6 gWater
Above average for vegetables
Onions are 309 kcal per 100 g. The 240 vegetables in this database average 59.9.
Onions309
Vegetables average59.9
High in fibre
19.3 g of fibre per 100 g; the UK “high fibre” line is 6 g.
Fibre, per portion15.4 g
Protein, per portion7 g
Vitamins and minerals in onions
Five of the 18 recorded reach the “high in” level. Potassium leads by a long way.
Only a trace
- Riboflavin
None recorded
- Vitamin D
- Vitamin B12
Show all 18 with amounts
Potassium967 mg, 48 %
Manganese0.72 mg, 36 %
Vitamin C26.4 mg, 33 %
Copper0.28 mg, 28 %
Calcium210 mg, 26 %
Phosphorus161 mg, 23 %
Vitamin E2 mg, 17 %
Thiamin (vitamin B1)0.18 mg, 17 %
Niacin (vitamin B3)2.6 mg, 16 %
Iron2.1 mg, 15 %
Magnesium55.2 mg, 15 %
Chloride104 mg, 13 %
Zinc0.96 mg, 9.6 %
Pantothenic acid (vitamin B5)0.56 mg, 9.3 %
Iodine0.0128 mg, 8.5 %
Vitamin A0.012 mg, 1.5 %
Vitamin Dnone recorded
Vitamin B12none recorded
Badges use the UK legal thresholds per 100 g: 15 % of the reference intake for “source of”, 30 % for “high in”. A trace is shown as “trace” and never counts.
What onions don’t give you. And where to find it.
No recorded vitamin D, riboflavin or vitamin B12.
Vitamin D
0mgin onions
Find it inBloater, grilled500 % per 100 g
Riboflavin (vitamin B2)
Tracein onions
Find it inLiver, lamb, fried404 % per 100 g
Vitamin B12
0mgin onions
Find it inLiver, ox, raw4400 % per 100 g
100 mgVitamin C, 125 %
0.075 mgSelenium, 136 %
0.00125 mgVitamin D, 25 %
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Onions against other vegetables
Per 100 g, onions have the most potassium of the 6 here, ahead of mushrooms (Jew's ear, tough, dried, raw).
1209mg
630mg
375mg
370mg
340mg
330mg
Onions, dried, rawthis page
Sweet potato, boiled−834 mg
Radish leaves, raw−839 mg
Kohl rabi, raw−869 mg
Gourd, karela, raw−879 mg
All values per 100 g, from the same dataset. Differences are against onions.
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Questions about onions
What the numbers say to the questions people actually search.
How many calories are in a portion of onions?
A typical portion (80 g, one of your five a day) gives 247 kcal. Per 100 g the figure is 309 kcal.
Is onions high in potassium?
Yes. Onions, dried, raw have 1209 mg potassium per 100 g, 60 % of the NRV, above the 30 % threshold for a “high in” claim.
Which vitamins and minerals do onions have most of?
By share of the daily reference intake: potassium (1209 mg, 60 %), manganese (0.9 mg, 45 %) and vitamin C (33 mg, 41 %) per 100 g.
Are onions high in fibre?
Yes. 19.3 g fibre per 100 g meets the UK “high fibre” threshold of 6 g.
How these numbers were made
Every figure comes from the UK Composition of Foods Integrated Dataset (CoFID), 2021 edition, record 13-590, Onions, dried, raw, published by Public Health England under the Open Government Licence v3.0. Main data references: DH, Nutrient analysis of fruit and vegetables, 2013; industry data, 2014 and estimated from 13-308. Values are per 100 g of the edible part; a portion is 80 g, one of your five a day, the usual UK portion for vegetables. Reference intakes follow Regulation (EU) 1169/2011 Annex XIII as retained in GB law; “source of”, “high in” and “low” follow Regulation (EC) 1924/2006, assessed per 100 g. Function lines are the authorised wording from the GB register of nutrition and health claims, credited to the nutrient. Energy is rounded to the whole kcal and kJ; other amounts to one decimal, or two below 1. A trace is shown as “trace” and never gets a figure or a badge; a nutrient never analysed is left off the page. We start from the dataset’s 2,887 records and keep 2,322: records weighed with bone, shell or skin, alcoholic drinks, infant foods, brand-named products, records with fewer than eight measured vitamins and minerals and near-identical variants are left out. Group context uses the 240 vegetables kept from the dataset; a rank counts only the foods with a measured figure for that nutrient. Food images are illustrations from Ingredient Atlas, released under CC0; they show the food, not the measured sample, and where no illustration of the exact food exists the nearest one is shown (here: Onion). Checked 5 October 2026. Contains public sector information licensed under the Open Government Licence v3.0.
More vegetables
From the same group, with calories per 100 g, and the foods with the most potassium.
More vegetables
- Cabbage, Chinese, raw12 kcal
- Courgette, fried in butter63 kcal
- Lotus tubers, raw51 kcal
- Pak choi, steamed14 kcal
- Pumpkin, boiled12 kcal
- Swede, raw24 kcal
- All 240 vegetables
Most potassium
- Courgette, dried6104 mg
- Spinach, dried4350 mg
- Mushroom, dried3870 mg
- Chervil, dried4740 mg
- Coriander leaves, dried4470 mg
- Parsley, dried4090 mg
- Potassium guide