8 %
Thiamin is below the 15 % “source of” level in onions, so no function line applies.
How many calories are in baked onions?
34.4kcal
in an 80 g portion
43 kcal per 100 g.
Source: UK CoFID 2021, record 13-589. Checked 5 October 2026.
0.16 gFat
0.96 gProtein
2.2 gFibre
8 %Daily thiamin
What’s in an 80 g portion
More than half of a portion is water. The rest is 7.9 g carbohydrate and 2.2 g fibre.
- 0.16 gFat
- 0.96 gProtein
- 7.9 gCarbohydrate
- 2.2 gFibre
- 69.1 gWater
Below average for vegetables
Onions are 43 kcal per 100 g. The 240 vegetables in this database average 59.9.
Onions43
Vegetables average59.9
Low in fat
0.2 g of fat per 100 g; the UK “low fat” line is 3 g.
Fat, per portion0.16 g
Vitamins and minerals in onions
No vitamin or mineral in onions reaches the “source of” level; thiamin is the nearest at 10 %.
Only a trace
- Selenium
None recorded
- Vitamin D
- Vitamin B12
Show all 22 with amounts
Thiamin (vitamin B1)0.09 mg, 8 %
Potassium138 mg, 6.9 %
Chloride53.6 mg, 6.7 %
Vitamin B60.08 mg, 5.7 %
Manganese0.1 mg, 4.8 %
Folate0.0088 mg, 4.4 %
Copper0.04 mg, 4 %
Calcium29.6 mg, 3.7 %
Phosphorus23.2 mg, 3.3 %
Vitamin C2.4 mg, 3 %
Niacin (vitamin B3)0.48 mg, 3 %
Vitamin E0.29 mg, 2.4 %
Magnesium8 mg, 2.1 %
Iron0.3 mg, 2.1 %
Biotin0.0008 mg, 1.6 %
Zinc0.16 mg, 1.6 %
Riboflavin (vitamin B2)0.02 mg, 1.1 %
Iodine0.0016 mg, 1.1 %
Pantothenic acid (vitamin B5)0.03 mg, 0.5 %
Vitamin A0.0016 mg, <1 %
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 or selenium, and only 2 % of the zinc reference intake per 100 g.
Vitamin D
0mgin onions
Find it inBloater, grilled500 % per 100 g
Selenium
Tracein onions
Find it inKidney, pig, fried491 % per 100 g
Zinc
2%in onions, per 100 g
Find it inOysters, raw592 % per 100 g
100 mgVitamin C, 125 %
0.075 mgSelenium, 136 %
0.00125 mgVitamin D, 25 %
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Onions against other vegetables
Onions come second for thiamin here, just behind parsnip (raw).
0.2mg
0.1mg
0.1mg
0.1mg
0.1mg
0mg
Parsnip, raw+0.1 mg
Onions, bakedthis page
Kohl rabi, boiled−0 mg
Marrow, parwal, raw−0.1 mg
Taro, steamed−0.1 mg
Shallots, raw−0.1 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 34 kcal. Per 100 g the figure is 43 kcal.
Does baking change the sodium in onions?
Yes. Per 100 g, sodium goes from 100 mg raw to 4 mg baked. Part of that is the vitamin or mineral itself changing, part is the change in water content.
Which vitamins and minerals do onions have most of?
By share of the daily reference intake: thiamin (0.11 mg, 10 %), potassium (172 mg, 8.6 %) and chloride (67 mg, 8.4 %) per 100 g.
Are onions high in salt?
No. Salt is 0.01 g per 100 g, which is very low under UK rules.
How these numbers were made
Every figure comes from the UK Composition of Foods Integrated Dataset (CoFID), 2021 edition, record 13-589, Onions, baked, published by Public Health England under the Open Government Licence v3.0. Main data references: DH, Nutrient analysis of fruit and vegetables, 2013. 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. The dataset's sample note is not shown on the page (its wording trips the site's checks). 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.
More vegetables
- Peas, boiled79 kcal
- Rape leaves, raw37 kcal
- Sweetcorn kernels, canned in water, drained78 kcal
- Amaranth leaves, boiled16 kcal
- Cabbage, red, raw21 kcal
- Cucumber, raw14 kcal
- All 240 vegetables