Vitamin IU to Mcg Converter
Convert a vitamin label quantity between IU and micrograms. Select the exact vitamin form because IU is a measure of biological activity and its mass conversion is not universal.
Converted quantity
— mcg
- Entered
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- Factor
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Unit conversion only: This result does not recommend a dose or assess whether a supplement is appropriate.
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How to convert vitamin IU to mcg
An International Unit (IU) represents biological activity, so there is no single IU-to-microgram factor for every nutrient. This converter applies the factor for the vitamin form you select and reverses the same arithmetic for mcg-to-IU conversions.
For vitamin D2 or D3, 1 IU equals 0.025 mcg. For vitamin A, FDA label conversions depend on the source: 1 IU equals 0.3 mcg RAE for preformed retinol or purified supplemental beta-carotene in oil, 0.05 mcg RAE for dietary beta-carotene, or 0.025 mcg RAE for dietary alpha-carotene or beta-cryptoxanthin. A mixed vitamin A total cannot be converted accurately unless its forms or proportions are known.
For vitamin E alpha-tocopherol, 1 IU equals 670 mcg for natural RRR-alpha-tocopherol and 450 mcg for synthetic all-rac-alpha-tocopherol. These vitamin E factors do not apply to unspecified mixed tocopherols, gamma-tocopherol, or tocotrienols.
Micrograms = IU × selected factor; IU = micrograms ÷ selected factor This converts label units only. It does not recommend a dose, determine equivalence between products, or assess whether a supplement is appropriate.
FDA: Converting Units of Measure for Folate, Niacin, and Vitamins A, D, and E ↗NIH Office of Dietary Supplements: Vitamin D ↗NIH Office of Dietary Supplements: Vitamin E ↗
Frequently asked questions
Is there one IU to mcg conversion factor?
No. IU represents biological activity, and the mass represented by one IU depends on the vitamin and sometimes its form. Select the form shown on the label.
How many mcg is 1,000 IU of vitamin D?
Using the FDA factor of 0.025 mcg per IU, 1,000 IU of vitamin D2 or D3 converts to 25 mcg. This arithmetic is not a dosage recommendation.
Why does vitamin A have several choices?
Preformed vitamin A and provitamin A carotenoids have different label conversion factors. A mixed total needs known forms or proportions, so this tool does not offer an unspecified vitamin A option.
Why are there natural and synthetic vitamin E choices?
FDA label guidance uses different factors for natural RRR-alpha-tocopherol and synthetic all-rac-alpha-tocopherol. The label may also use the prefixes d-alpha and dl-alpha, respectively.
Does this converter tell me how much vitamin to take?
No. It only converts a quantity you enter. It does not recommend a dose or evaluate safety, need, or product quality.