Health Calculators
Supplement label units.
Supplement labels mix IU, mcg RAE, mcg DFE and mg NE. Pick the vitamin and direction, enter the amount and get the converted figure using the NIH Office of Dietary Supplements factors. Runs in your browser; nothing is sent anywhere.
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Converted amount
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Worked example
1,000 IU of vitamin D ÷ 40 = 25 mcg. 5,000 IU of preformed vitamin A (retinol) × 0.3 = 1,500 mcg RAE. 400 IU of natural vitamin E × 0.67 = 268 mg. 400 mcg of folic acid taken with food ÷ 0.6 = 666.7 mcg DFE, or 800 mcg DFE if taken on an empty stomach (÷ 0.5).
How it works
Factors from the NIH Office of Dietary Supplements fact sheets: vitamin D 1 mcg = 40 IU. Vitamin A converts to mcg RAE by source: 1 IU retinol = 0.3 mcg RAE, 1 IU supplemental beta-carotene = 0.3, 1 IU dietary beta-carotene = 0.05, 1 IU dietary alpha-carotene or beta-cryptoxanthin = 0.025. Vitamin E: 1 IU natural = 0.67 mg alpha-tocopherol, 1 IU synthetic = 0.45 mg; going the other way, 1 mg = 1.49 IU natural or 2.22 IU synthetic. Folate: 1 mcg DFE = 1 mcg food folate = 0.6 mcg folic acid from fortified foods or supplements with food = 0.5 mcg folic acid from supplements on an empty stomach. Niacin: 1 mg NE = 1 mg niacin = 60 mg tryptophan.
Vitamin A only converts between IU and RAE if you know the source. The tool does not convert 5-MTHF folate, because the fact sheet says those factors have not been formally established. The reverse vitamin E factors are the rounded values the fact sheet gives, so a round trip can differ slightly.
Sources (opened 2026-10-08): NIH ODS, Vitamin D; NIH ODS, Vitamin A and Carotenoids; NIH ODS, Vitamin E; NIH ODS, Folate; NIH ODS, Niacin.
FAQ
How do I convert IU to mcg for vitamin D?
Divide IU by 40. 1 mcg of vitamin D equals 40 IU, so 1,000 IU is 25 mcg and 4,000 IU is 100 mcg.
How do I convert vitamin A IU to mcg RAE?
It depends on the source. 1 IU of retinol or supplemental beta-carotene is 0.3 mcg RAE, 1 IU of beta-carotene from food is 0.05 mcg RAE, and 1 IU of dietary alpha-carotene or beta-cryptoxanthin is 0.025 mcg RAE.
What is mcg DFE on a folate label?
DFE means dietary folate equivalents. 1 mcg DFE equals 1 mcg of food folate, 0.6 mcg of folic acid taken with food, or 0.5 mcg of folic acid taken on an empty stomach.
Can I use this to choose a dose?
No. It only converts units. Upper limits apply, and some vitamins interact with medicines, so check with a pharmacist or doctor before taking supplements.
This converts the dose on the bottle. For blood test results use the vitamin D blood level converter.
Disclaimer
Not medical advice. Upper limits differ by age and life stage; check with a pharmacist if you take medication. Converting units does not tell you whether a dose is right for you.