Ask Login. Today, many countries still use the IU to measure vitamin D; 1 IU of vitamin D is equivalent to 0.025 micrograms (abbreviated as either mcg or μg) of cholecalciferol or ergocalciferol.1 Conversely, 1 microgram of vitamin D equals 40 IU of vitamin D. Once vitamin D3 could be made by scientists, the IU recommendation was changed to be based off vitamin D3 in 1949. 400 IU vitamin D equals. Vitamin D Wiki User Answered . Answer. Vitamin E. New guidelines require that Vitamin E content be determined based on the source of vitamin E and that it be reported as mg alpha-tocopherol rather than in IU. Vitamin E in food and dietary supplements can come from natural or synthetic forms. Asked by Wiki User. Vitamin D intake is recommended at 400–800 IU/day, or 10–20 micrograms. For example: 400 IU of vitamin E as d-alpha * 0.67 = 268 mg vitamin E. To go the other way you just divide: ... Units of Measure. To convert from IU to mg alpha-tocopherol, use the 2 steps listed in the table, above. https://www.thecalculatorsite.com/articles/units/convert-ui-to-mcg.php The convention is to measure vitamin D (which in 99% of cases is vitamin D3 or cholecalciferol) in International Units: Cholecalciferol medical facts from Drugs.com. 400 IU vitamin D equals how many milligrams? 180 mg vitamin E at dl-alpha / 0.45 = 400 IU vitamin E. If it’s a naturally-sourced vitamin E, you will see it called “d-alpha.” If you see “d-alpha” on the label, just multiply the IU by 0.67. Vitamin D is measured in micrograms (mcg) not milligrams (mg). 46 47 48. Top Answer.