IU to mg Converter
Convert between International Units and milligrams for vitamins and medications. Enter values for instant results with step-by-step formulas.
Reviewed by Manoj Kumar, Mathematics Educator
Formula
Mass = IU x Conversion Factor (substance-specific)
International Units measure biological activity, not mass. Each substance has a unique conversion factor defined by WHO. For example, Vitamin D: 1 IU = 0.025 mcg; Vitamin E (natural): 1 IU = 0.67 mg; Vitamin A (retinol): 1 IU = 0.3 mcg.
Worked Examples
Example 1: Vitamin D Supplement Conversion
Problem:Convert a 5,000 IU Vitamin D3 supplement to micrograms and milligrams.
Solution:Conversion factor: 1 IU Vitamin D = 0.025 mcg\nmcg = 5,000 IU x 0.025 = 125 mcg\nmg = 125 mcg / 1,000 = 0.125 mg\nVerification: 0.125 mg x 40,000 IU/mg = 5,000 IU (correct)
Result:5,000 IU of Vitamin D3 = 125 mcg = 0.125 mg
Example 2: Natural vs Synthetic Vitamin E
Problem:Compare 400 IU of natural vs synthetic Vitamin E in milligrams.
Solution:Natural (d-alpha): 400 IU x 0.67 mg/IU = 268 mg\nSynthetic (dl-alpha): 400 IU x 0.45 mg/IU = 180 mg\nDifference: 268 - 180 = 88 mg more in natural form\nNatural has 49% more mass per IU due to higher bioactivity
Result:400 IU natural = 268 mg | 400 IU synthetic = 180 mg (88 mg difference)
References
Reviewed by Manoj Kumar, Mathematics Educator · Editorial policy