Onions may not be the first food that comes to mind when you think of vitamin C, but they contribute a quiet, steady supply of this essential nutrient. A 100 g serving of raw onion provides about 7.4 mg of vitamin C — roughly 8% of the Daily Value — and scallions (spring onions) pack more than twice that amount. Because most recipes use onions by the slice, cup, or whole bulb, it can be hard to know exactly how much vitamin C ends up on your plate. This calculator turns any onion amount into a precise milligram value.
Nutrition students, meal planners, and home cooks can all use it to compare raw and cooked onion forms, scale up recipes, or check whether a side of onions meaningfully contributes to daily vitamin C needs. Just choose the type of onion, enter the amount, and you will get the vitamin C content, serving weight, and percent Daily Value instantly.
📊 Vitamin C result
Why Onion Vitamin C Counts
Onions are not a vitamin C powerhouse like citrus fruits, but they make a useful contribution to daily intake when eaten regularly. A 100 g serving of raw onion — roughly two-thirds of a medium bulb — supplies about 7.4 mg of vitamin C, or 8% of the Daily Value used by the FDA for adults. Spring onions and scallions are a different story: the same 100 g serving provides about 18.8 mg, which covers more than 20% of the daily target.
Because onions appear in so many cuisines, their vitamin C adds up across a day. The amount you actually get depends on the variety, the portion, and how the onion is prepared. Cooking in water can leach vitamin C into the cooking liquid, and high heat speeds up its breakdown. That is why the calculator includes both raw and boiled onion forms and lets you choose real-world portion units such as cups, tablespoons, and whole bulbs.
How the Calculator Works
The calculator uses nutrient values from USDA FoodData Central. Total vitamin C is found with this formula:
Vitamin C (mg) = serving weight in grams × (mg vitamin C per 100 g ÷ 100)
For whole-bulb and spoon units, the calculator first converts the amount to grams using average food portion weights: 1 cup chopped onion ≈ 160 g; 1 medium onion ≈ 110 g; 1 large onion ≈ 150 g; 1 tablespoon chopped onion ≈ 10 g. These are common reference weights used in nutrition analysis and recipe scaling, but a tightly packed cup or an unusually large bulb can shift the result by a few grams.
The Daily Value percentage is based on 90 mg per day, the FDA adult reference for vitamin C. If you are following a different personal target, take the milligram result, multiply by 100, and divide by your target to get your own percentage.
Reference Table: Vitamin C in Common Onion Forms
| Onion form | mg per 100 g | % DV per 100 g |
|---|---|---|
| Raw yellow/white onion | 7.4 | 8% |
| Raw red onion | 7.4 | 8% |
| Spring onion / scallion (raw) | 18.8 | 21% |
| Cooked / boiled onion | 5.2 | 6% |
Data are from USDA FoodData Central entries for raw onions, red onions, spring onions, and boiled yellow onions. Red onions are similar to white and yellow onions in vitamin C, but they contain extra anthocyanin pigments that act as antioxidants. The spring onion value includes both the white bulb and the green tops.
Worked Examples
1 medium raw onion (110 g)
110 g × 7.4 mg ÷ 100 = 8.1 mg vitamin C, about 9% of the Daily Value.
1 cup chopped raw onion (160 g)
160 g × 7.4 mg ÷ 100 = 11.8 mg vitamin C, about 13% of the Daily Value.
100 g spring onions / scallions
100 g × 18.8 mg ÷ 100 = 18.8 mg vitamin C, about 21% of the Daily Value.
Tips for Getting the Most Vitamin C from Onions
If you are pairing onions with iron-rich plant foods, their vitamin C is a useful bonus: vitamin C can improve absorption of non-heme iron from beans, lentils, and leafy greens when eaten in the same meal.
Frequently Asked Questions
Are red onions higher in vitamin C than yellow or white onions?
According to USDA data, raw red onions average around 7.4 mg per 100 g, similar to yellow and white onions. The bigger difference is color: red onions contain anthocyanins, which are antioxidant pigments, not vitamin C.
Does cooking destroy all the vitamin C in onions?
No, but it reduces it. Boiling can lower the content to about 5.2 mg per 100 g because some vitamin C dissolves into the water and heat accelerates breakdown. To retain more, use gentle cooking methods or save the cooking liquid in soups and sauces.
How many onions would I need to meet the full 90 mg Daily Value?
For raw onion at 7.4 mg per 100 g, you would need about 1.2 kg — roughly 11 medium onions — to reach 90 mg. That is impractical, so onions are best treated as a supporting source alongside high-vitamin C foods such as peppers, broccoli, and citrus.
Can I use this calculator for a recipe?
Yes. Sum the vitamin C from each onion-containing ingredient, then divide by the number of servings. If the onions are cooked, use the boiled value to account for typical losses.
For official intake guidance, see the NIH Vitamin C fact sheet. For food composition data, browse USDA FoodData Central. If you are comparing vitamin C in other packaged foods, the ham vitamin C calculator is another useful reference.