Vitamin D: IU to mcg converter
This IU to mcg converter turns vitamin D international units into micrograms and back: 1 mcg of vitamin D3 equals 40 IU, so 1,000 IU are 25 mcg and 2,000 IU are 50 mcg. It also flags amounts above the upper limit for ages 9 and older.
Example: I have the amount in: IU (international units) · Amount of vitamin D 1,000 → Conversion: 1,000 IU = 25 mcg (0.025 mg). Source: MedlinePlus (U.S. National Library of Medicine), „Vitamin D“: 1 µg Cholecalciferol (D3) = 40 IU; Zufuhrempfehlungen 400/600/800 IU (10/15/20 µg) und obere sichere Grenzen 1.000–4.000 IU (25–100 µg) je Alter; Überdosierung fast immer durch Präparate (gelesen 10.10.2026). Updated: .
How it is calculated
1 mcg of vitamin D = 40 IU, so IU ÷ 40 = mcg and mcg × 40 = IU. MedlinePlus, the consumer health service of the U.S. National Library of Medicine, states: one microgram of cholecalciferol (D3) is the same as 40 IU of vitamin D. A 1,000 IU softgel therefore contains 25 mcg, and 0.001 mg is the same as 1 mcg.
IU to mcg conversion table
| IU | mcg |
|---|---|
| 400 | 10 |
| 1,000 | 25 |
| 2,000 | 50 |
| 4,000 | 100 |
| 5,000 | 125 |
| 10,000 | 250 |
| 50,000 | 1,250 |
Daily intake and upper limits
MedlinePlus lists these amounts per day; the second column is IU, the third the same amount in mcg as printed there.
| Group | IU per day | mcg per day |
|---|---|---|
| Infants 0–12 months (adequate intake) | 400 | 10 |
| Children, teens and adults 1–70 years, pregnancy and breastfeeding | 600 | 15 |
| Adults over 70 | 800 | 20 |
| Upper limit, infants 0–6 months | 1,000 | 25 |
| Upper limit, infants 7–12 months | 1,500 | 38 |
| Upper limit, children 1–3 years | 2,500 | 63 |
| Upper limit, children 4–8 years | 3,000 | 75 |
| Upper limit, 9 years and older | 4,000 | 100 |
1,500 IU are exactly 37.5 mcg and 2,500 IU are 62.5 mcg; MedlinePlus rounds them to 38 and 63.
Labels and safety
- On U.S. Nutrition and Supplement Facts labels vitamin D must be declared in mcg; IU may follow in parentheses (21 CFR 101.9).
- MedlinePlus warns that vitamin D toxicity almost always comes from taking too many supplements: too much vitamin D can make the intestines absorb too much calcium, which may raise the calcium level in the blood.
- Count every product you take – for example multivitamins and drops – when you compare with the limits, and ask your doctor which amount is right for you.
For other daily amounts see the caffeine calculator and the TDEE calculator; grams and kilograms convert with grams to kg.
Frequently asked questions
How many mcg is 1,000 IU of vitamin D?
25 mcg. Divide the IU by 40: 1,000 ÷ 40 = 25.
How many IU is 50 mcg of vitamin D?
2,000 IU. Multiply the micrograms by 40: 50 × 40 = 2,000.
Is 5,000 IU of vitamin D too much?
5,000 IU are 125 mcg, which is above the 4,000 IU (100 mcg) a day that MedlinePlus gives as the safe upper limit for ages 9 and older. Do not take that much without medical advice.
How many IU is 10 mcg of vitamin D?
400 IU – the daily adequate intake for infants up to 12 months in the MedlinePlus table.
Does the factor 40 work for vitamin A or E?
No. 1 mcg = 40 IU is the vitamin D factor. Vitamins A and E use different conversions, so this converter is only for vitamin D.
Sources and legal basis
- MedlinePlus (U.S. National Library of Medicine), „Vitamin D“: 1 µg Cholecalciferol (D3) = 40 IU; Zufuhrempfehlungen 400/600/800 IU (10/15/20 µg) und obere sichere Grenzen 1.000–4.000 IU (25–100 µg) je Alter; Überdosierung fast immer durch Präparate (gelesen 10.10.2026)
- eCFR, 21 CFR 101.9 Nutrition labeling of food: Vitamin D in Mikrogramm (mcg), IU nur zusätzlich in Klammern nach der mcg-Angabe (gelesen 10.10.2026)
As of: · Editorial policy
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